In the descriptions here, a parameter or return value of NULL means NULL in the sense of the C programming language, not a MySQL NULL value.
Functions that return a value generally return a pointer or an integer. Unless specified otherwise, functions returning a pointer return a non-NULL value to indicate success or a NULL value to indicate an error, and functions returning an integer return zero to indicate success or non-zero to indicate an error. Note that ``non-zero'' means just that. Unless the function description says otherwise, do not test against a value other than zero:
if (result) /* correct */ ... error ... if (result < 0) /* incorrect */ ... error ... if (result == -1) /* incorrect */ ... error ...
When a function returns an error, the Errors subsection of the function description lists the possible types of errors. You can find out which of these occurred by calling mysql_errno(). A string representation of the error may be obtained by calling mysql_error().
Returns the number of rows changed by the last UPDATE, deleted by the last DELETE or inserted by the last INSERT statement. May be called immediately after mysql_query() for UPDATE, DELETE, or INSERT statements. For SELECT statements, mysql_affected_rows() works like mysql_num_rows().
An integer greater than zero indicates the number of rows affected or retrieved. Zero indicates that no records where updated for an UPDATE statement, no rows matched the WHERE clause in the query or that no query has yet been executed. -1 indicates that the query returned an error or that, for a SELECT query, mysql_affected_rows() was called prior to calling mysql_store_result(). Because mysql_affected_rows() returns an unsigned value, you can check for -1 by comparing the return value to (my_ulonglong)-1 (or to (my_ulonglong)~0, which is equivalent).
mysql_query(&mysql,"UPDATE products SET cost=cost*1.25 WHERE group=10"); printf("%ld products updated",(long) mysql_affected_rows(&mysql));
If one specifies the flag CLIENT_FOUND_ROWS when connecting to mysqld, mysql_affected_rows() will return the number of rows matched by the WHERE statement for UPDATE statements.
Note that when one uses a REPLACE command, mysql_affected_rows() will return 2 if the new row replaced and old row. This is because in this case one row was inserted after the duplicate was deleted.
Changes the user and causes the database specified by db to become the default (current) database on the connection specified by mysql. In subsequent queries, this database is the default for table references that do not include an explicit database specifier.
This function was introduced in MySQL Version 3.23.3.
mysql_change_user() fails unless the connected user can be authenticated or if he doesn't have permission to use the database. In this case the user and database are not changed
The db parameter may be set to NULL if you don't want to have a default database.
Starting from MySQL 4.0.6 this command will always ROLLBACK any active transactions, close all temporary tables, unlock all locked tables and reset the state as if one had done a new connect. This will happen even if the user didn't change.
The same that you can get from mysql_real_connect().
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
ER_UNKNOWN_COM_ERROR | The MySQL server doesn't implement this command (probably an old server). |
ER_ACCESS_DENIED_ERROR | The user or password was wrong. |
ER_BAD_DB_ERROR | The database didn't exist. |
ER_DBACCESS_DENIED_ERROR | The user did not have access rights to the database. |
ER_WRONG_DB_NAME | The database name was too long. |
if (mysql_change_user(&mysql, "user", "password", "new_database")) { fprintf(stderr, "Failed to change user. Error: %s\n", mysql_error(&mysql)); }
Closes a previously opened connection. mysql_close() also deallocates the connection handle pointed to by mysql if the handle was allocated automatically by mysql_init() or mysql_connect().
This function is deprecated. It is preferable to use mysql_real_connect() instead.
mysql_connect() attempts to establish a connection to a MySQL database engine running on host. mysql_connect() must complete successfully before you can execute any of the other API functions, with the exception of mysql_get_client_info().
The meanings of the parameters are the same as for the corresponding parameters for mysql_real_connect() with the difference that the connection parameter may be NULL. In this case the C API allocates memory for the connection structure automatically and frees it when you call mysql_close(). The disadvantage of this approach is that you can't retrieve an error message if the connection fails. (To get error information from mysql_errno() or mysql_error(), you must provide a valid MYSQL pointer.)
Creates the database named by the db parameter.
This function is deprecated. It is preferable to use mysql_query() to issue an SQL CREATE DATABASE statement instead.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
if(mysql_create_db(&mysql, "my_database")) { fprintf(stderr, "Failed to create new database. Error: %s\n", mysql_error(&mysql)); }
Seeks to an arbitrary row in a query result set. The offset value is a row number and should be in the range from 0 to mysql_num_rows(stmt)-1.
This function requires that the result set structure contains the entire result of the query, so mysql_data_seek() may be used only in conjunction with mysql_store_result(), not with mysql_use_result().
Does a DBUG_PUSH with the given string. mysql_debug() uses the Fred Fish debug library. To use this function, you must compile the client library to support debugging. See Debugging server. See Debugging client.
The call shown here causes the client library to generate a trace file in /tmp/client.trace on the client machine:
mysql_debug("d:t:O,/tmp/client.trace");
Drops the database named by the db parameter.
This function is deprecated. It is preferable to use mysql_query() to issue an SQL DROP DATABASE statement instead.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
if(mysql_drop_db(&mysql, "my_database")) fprintf(stderr, "Failed to drop the database: Error: %s\n", mysql_error(&mysql));
Instructs the server to write some debug information to the log. For this to work, the connected user must have the SUPER privilege.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
This function is deprecated. mysql_errno() or mysql_error() may be used instead.
mysql_eof() determines whether the last row of a result set has been read.
If you acquire a result set from a successful call to mysql_store_result(), the client receives the entire set in one operation. In this case, a NULL return from mysql_fetch_row() always means the end of the result set has been reached and it is unnecessary to call mysql_eof(). When used with mysql_store_result(), mysql_eof() will always return true.
On the other hand, if you use mysql_use_result() to initiate a result set retrieval, the rows of the set are obtained from the server one by one as you call mysql_fetch_row() repeatedly. Because an error may occur on the connection during this process, a NULL return value from mysql_fetch_row() does not necessarily mean the end of the result set was reached normally. In this case, you can use mysql_eof() to determine what happened. mysql_eof() returns a non-zero value if the end of the result set was reached and zero if an error occurred.
Historically, mysql_eof() predates the standard MySQL error functions mysql_errno() and mysql_error(). Because those error functions provide the same information, their use is preferred over mysql_eof(), which is now deprecated. (In fact, they provide more information, because mysql_eof() returns only a boolean value whereas the error functions indicate a reason for the error when one occurs.)
The following example shows how you might use mysql_eof():
mysql_query(&mysql,"SELECT * FROM some_table"); result = mysql_use_result(&mysql); while((row = mysql_fetch_row(result))) { // do something with data } if(!mysql_eof(result)) // mysql_fetch_row() failed due to an error { fprintf(stderr, "Error: %s\n", mysql_error(&mysql)); }
However, you can achieve the same effect with the standard MySQL error functions:
mysql_query(&mysql,"SELECT * FROM some_table"); result = mysql_use_result(&mysql); while((row = mysql_fetch_row(result))) { // do something with data } if(mysql_errno(&mysql)) // mysql_fetch_row() failed due to an error { fprintf(stderr, "Error: %s\n", mysql_error(&mysql)); }
For the connection specified by mysql, mysql_errno() returns the error code for the most recently invoked API function that can succeed or fail. A return value of zero means that no error occurred. Client error message numbers are listed in the MySQL errmsg.h header file. Server error message numbers are listed in mysqld_error.h. In the MySQL source distribution you can find a complete list of error messages and error numbers in the file Docs/mysqld_error.txt. The server error codes also are listed at Error-returns.
Note that some functions like mysql_fetch_row() don't set mysql_errno() if they succeed.
A rule of thumb is that all functions that have to ask the server for information will reset mysql_errno() if they succeed.
An error code value for the last mysql_xxx call, if it failed. zero means no error occurred.
For the connection specified by mysql, mysql_error() returns a null-terminated string containing the error message for the most recently invoked API function that failed. If a function didn't fail, the return value of mysql_error() may be the previous error or an empty string to indicate no error.
A rule of thumb is that all functions that have to ask the server for information will reset mysql_error() if they succeed.
For functions that resets mysql_errno, the following two tests are equivalent:
if(mysql_errno(&mysql)) { // an error occurred } if(mysql_error(&mysql)[0] != '\0') { // an error occurred }
The language of the client error messages may be changed by recompiling the MySQL client library. Currently you can choose error messages in several different languages. See Languages.
A null-terminated character string that describes the error. An empty string if no error occurred.
Returns the definition of one column of a result set as a MYSQL_FIELD structure. Call this function repeatedly to retrieve information about all columns in the result set. mysql_fetch_field() returns NULL when no more fields are left.
mysql_fetch_field() is reset to return information about the first field each time you execute a new SELECT query. The field returned by mysql_fetch_field() is also affected by calls to mysql_field_seek().
If you've called mysql_query() to perform a SELECT on a table but have not called mysql_store_result(), MySQL returns the default blob length (8K bytes) if you call mysql_fetch_field() to ask for the length of a BLOB field. (The 8K size is chosen because MySQL doesn't know the maximum length for the BLOB. This should be made configurable sometime.) Once you've retrieved the result set, field->max_length contains the length of the largest value for this column in the specific query.
MYSQL_FIELD *field; while((field = mysql_fetch_field(result))) { printf("field name %s\n", field->name); }
Returns an array of all MYSQL_FIELD structures for a result set. Each structure provides the field definition for one column of the result set.
unsigned int num_fields; unsigned int i; MYSQL_FIELD *fields; num_fields = mysql_num_fields(result); fields = mysql_fetch_fields(result); for(i = 0; i < num_fields; i++) { printf("Field %u is %s\n", i, fields[i].name); }
Given a field number fieldnr for a column within a result set, returns that column's field definition as a MYSQL_FIELD structure. You may use this function to retrieve the definition for an arbitrary column. The value of fieldnr should be in the range from 0 to mysql_num_fields(result)-1.
unsigned int num_fields; unsigned int i; MYSQL_FIELD *field; num_fields = mysql_num_fields(result); for(i = 0; i < num_fields; i++) { field = mysql_fetch_field_direct(result, i); printf("Field %u is %s\n", i, field->name); }
Returns the lengths of the columns of the current row within a result set. If you plan to copy field values, this length information is also useful for optimization, because you can avoid calling strlen(). In addition, if the result set contains binary data, you must use this function to determine the size of the data, because strlen() returns incorrect results for any field containing null characters.
The length for empty columns and for columns containing NULL values is zero. To see how to distinguish these two cases, see the description for mysql_fetch_row().
An array of unsigned long integers representing the size of each column (not including any terminating null characters). NULL if an error occurred.
mysql_fetch_lengths() is valid only for the current row of the result set. It returns NULL if you call it before calling mysql_fetch_row() or after retrieving all rows in the result.
MYSQL_ROW row; unsigned long *lengths; unsigned int num_fields; unsigned int i; row = mysql_fetch_row(result); if (row) { num_fields = mysql_num_fields(result); lengths = mysql_fetch_lengths(result); for(i = 0; i < num_fields; i++) { printf("Column %u is %lu bytes in length.\n", i, lengths[i]); } }
Retrieves the next row of a result set. When used after mysql_store_result(), mysql_fetch_row() returns NULL when there are no more rows to retrieve. When used after mysql_use_result(), mysql_fetch_row() returns NULL when there are no more rows to retrieve or if an error occurred.
The number of values in the row is given by mysql_num_fields(result). If row holds the return value from a call to mysql_fetch_row(), pointers to the values are accessed as row[0] to row[mysql_num_fields(result)-1]. NULL values in the row are indicated by NULL pointers.
The lengths of the field values in the row may be obtained by calling mysql_fetch_lengths(). Empty fields and fields containing NULL both have length 0; you can distinguish these by checking the pointer for the field value. If the pointer is NULL, the field is NULL; otherwise, the field is empty.
A MYSQL_ROW structure for the next row. NULL if there are no more rows to retrieve or if an error occurred.
Note that error is not reset between calls to mysql_fetch_row()
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
MYSQL_ROW row; unsigned int num_fields; unsigned int i; num_fields = mysql_num_fields(result); while ((row = mysql_fetch_row(result))) { unsigned long *lengths; lengths = mysql_fetch_lengths(result); for(i = 0; i < num_fields; i++) { printf("[%.*s] ", (int) lengths[i], row[i] ? row[i] : "NULL"); } printf("\n"); }
Returns the number of columns for the most recent query on the connection.
The normal use of this function is when mysql_store_result() returned NULL (and thus you have no result set pointer). In this case, you can call mysql_field_count() to determine whether mysql_store_result() should have produced a non-empty result. This allows the client program to take proper action without knowing whether the query was a SELECT (or SELECT-like) statement. The example shown here illustrates how this may be done.
MYSQL_RES *result; unsigned int num_fields; unsigned int num_rows; if (mysql_query(&mysql,query_string)) { // error } else // query succeeded, process any data returned by it { result = mysql_store_result(&mysql); if (result) // there are rows { num_fields = mysql_num_fields(result); // retrieve rows, then call mysql_free_result(result) } else // mysql_store_result() returned nothing; should it have? { if(mysql_field_count(&mysql) == 0) { // query does not return data // (it was not a SELECT) num_rows = mysql_affected_rows(&mysql); } else // mysql_store_result() should have returned data { fprintf(stderr, "Error: %s\n", mysql_error(&mysql)); } } }
An alternative is to replace the mysql_field_count(&mysql) call with mysql_errno(&mysql). In this case, you are checking directly for an error from mysql_store_result() rather than inferring from the value of mysql_field_count() whether the statement was a SELECT.
Sets the field cursor to the given offset. The next call to mysql_fetch_field() will retrieve the field definition of the column associated with that offset.
To seek to the beginning of a row, pass an offset value of zero.
Returns the position of the field cursor used for the last mysql_fetch_field(). This value can be used as an argument to mysql_field_seek().
Frees the memory allocated for a result set by mysql_store_result(), mysql_use_result(), mysql_list_dbs(), etc. When you are done with a result set, you must free the memory it uses by calling mysql_free_result().
Do not attempt to access a result set after freeing it.
Returns an integer that represents the client library version. The value has the format XYYZZ where X is the major version, YY is the release level, and ZZ is the version number within the release level. For example, a value of 40102 represents a client library version of 4.1.2.
Returns a string describing the type of connection in use, including the server hostname.
A number that represents the MySQL server version in format:
main_version*10000 + minor_version *100 + sub_version
For example, 4.1.0 is returned as 40100.
This is useful to quickly determine the version of the server in a client program to know if some capability exits.
Retrieves a string providing information about the most recently executed query, but only for the statements listed here. For other statements, mysql_info() returns NULL. The format of the string varies depending on the type of query, as described here. The numbers are illustrative only; the string will contain values appropriate for the query.
INSERT INTO ... SELECT ... | String format: Records: 100 Duplicates: 0 Warnings: 0 |
INSERT INTO ... VALUES (...),(...),(...)... | String format: Records: 3 Duplicates: 0 Warnings: 0 |
LOAD DATA INFILE ... | String format: Records: 1 Deleted: 0 Skipped: 0 Warnings: 0 |
ALTER TABLE | String format: Records: 3 Duplicates: 0 Warnings: 0 |
UPDATE | String format: Rows matched: 40 Changed: 40 Warnings: 0 |
Note that mysql_info() returns a non-NULL value for INSERT ... VALUES only for the multiple-row form of the statement (that is, only if multiple value lists are specified).
A character string representing additional information about the most recently executed query. NULL if no information is available for the query.
Allocates or initializes a MYSQL object suitable for mysql_real_connect(). If mysql is a NULL pointer, the function allocates, initializes, and returns a new object. Otherwise, the object is initialized and the address of the object is returned. If mysql_init() allocates a new object, it will be freed when mysql_close() is called to close the connection.
An initialized MYSQL* handle. NULL if there was insufficient memory to allocate a new object.
Returns the value generated for an AUTO_INCREMENT column by the previous INSERT or UPDATE query. Use this function after you have performed an INSERT query into a table that contains an AUTO_INCREMENT field.
Note that mysql_insert_id() returns 0 if the previous query does not use an AUTO_INCREMENT value. If you need to save the value for later, be sure to call mysql_insert_id() immediately after the query that generates the value.
If the previous query returned an error, the value of mysql_insert_id() is undefined.
mysql_insert_id() is updated after:
INSERT statements that sets or generates an AUTO_INCREMENT value. In case of multi-row INSERT statement mysql_insert_id() returns the FIRST generated AUTO_INCREMENT value or the LAST set AUTO_INCREMENT value if there was no generated value.
UPDATE statements that generate an AUTO_INCREMENT value.
INSERT or UPDATE statements that set a column value to LAST_INSERT_ID(expr).
Also note that the value of the SQL LAST_INSERT_ID() function always contains the most recently generated AUTO_INCREMENT value, and is not reset between queries because the value of that function is maintained in the server. Another difference is that LAST_INSERT_ID() is not updated if you set an AUTO_INCREMENT column to a specific value.
The reason for the difference between LAST_INSERT_ID() and mysql_insert_id() is that LAST_INSERT_ID() is made easy to use in scripts while mysql_insert_id() tries to provide a little more exact information of what happens to the auto_increment column.
The value of the AUTO_INCREMENT field that was updated by the previous query. Returns zero if there was no previous query on the connection or if the query did not update an AUTO_INCREMENT value.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Returns a result set consisting of database names on the server that match the simple regular expression specified by the wild parameter. wild may contain the wildcard characters % or _, or may be a NULL pointer to match all databases. Calling mysql_list_dbs() is similar to executing the query SHOW databases [LIKE wild].
You must free the result set with mysql_free_result().
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_OUT_OF_MEMORY | Out of memory. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Returns a result set consisting of field names in the given table that match the simple regular expression specified by the wild parameter. wild may contain the wildcard characters % or _, or may be a NULL pointer to match all fields. Calling mysql_list_fields() is similar to executing the query SHOW COLUMNS FROM tbl_name [LIKE wild].
Note that it's recommended that you use SHOW COLUMNS FROM tbl_name instead of mysql_list_fields().
You must free the result set with mysql_free_result().
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Returns a result set describing the current server threads. This is the same kind of information as that reported by mysqladmin processlist or a SHOW PROCESSLIST query.
You must free the result set with mysql_free_result().
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Returns a result set consisting of table names in the current database that match the simple regular expression specified by the wild parameter. wild may contain the wildcard characters % or _, or may be a NULL pointer to match all tables. Calling mysql_list_tables() is similar to executing the query SHOW tables [LIKE wild].
You must free the result set with mysql_free_result().
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Returns the number of columns in a result set.
Note that you can get the number of columns either from a pointer to a result set or to a connection handle. You would use the connection handle if mysql_store_result() or mysql_use_result() returned NULL (and thus you have no result set pointer). In this case, you can call mysql_field_count() to determine whether mysql_store_result() should have produced a non-empty result. This allows the client program to take proper action without knowing whether or not the query was a SELECT (or SELECT-like) statement. The example shown here illustrates how this may be done.
MYSQL_RES *result; unsigned int num_fields; unsigned int num_rows; if (mysql_query(&mysql,query_string)) { // error } else // query succeeded, process any data returned by it { result = mysql_store_result(&mysql); if (result) // there are rows { num_fields = mysql_num_fields(result); // retrieve rows, then call mysql_free_result(result) } else // mysql_store_result() returned nothing; should it have? { if (mysql_errno(&mysql)) { fprintf(stderr, "Error: %s\n", mysql_error(&mysql)); } else if (mysql_field_count(&mysql) == 0) { // query does not return data // (it was not a SELECT) num_rows = mysql_affected_rows(&mysql); } } }
An alternative (if you know that your query should have returned a result set) is to replace the mysql_errno(&mysql) call with a check if mysql_field_count(&mysql) is = 0. This will only happen if something went wrong.
Returns the number of rows in the result set.
The use of mysql_num_rows() depends on whether you use mysql_store_result() or mysql_use_result() to return the result set. If you use mysql_store_result(), mysql_num_rows() may be called immediately. If you use mysql_use_result(), mysql_num_rows() will not return the correct value until all the rows in the result set have been retrieved.
Can be used to set extra connect options and affect behavior for a connection. This function may be called multiple times to set several options.
mysql_options() should be called after mysql_init() and before mysql_connect() or mysql_real_connect().
The option argument is the option that you want to set; the arg argument is the value for the option. If the option is an integer, then arg should point to the value of the integer.
Possible options values:
Option | Argument type | Function |
MYSQL_OPT_CONNECT_TIMEOUT | unsigned int * | Connect timeout in seconds. |
MYSQL_OPT_READ_TIMEOUT | unsigned int * | Timeout for reads from server (works currently only on Windows on TCP/IP connections) |
MYSQL_OPT_WRITE_TIMEOUT | unsigned int * | Timeout for writes to server (works currently only on Windows on TCP/IP connections) |
MYSQL_OPT_COMPRESS | Not used | Use the compressed client/server protocol. |
MYSQL_OPT_LOCAL_INFILE | optional pointer to uint | If no pointer is given or if pointer points to an unsigned int != 0 the command LOAD LOCAL INFILE is enabled. |
MYSQL_OPT_NAMED_PIPE | Not used | Use named pipes to connect to a MySQL server on NT. |
MYSQL_INIT_COMMAND | char * | Command to execute when connecting to the MySQL server. Will automatically be re-executed when reconnecting. |
MYSQL_READ_DEFAULT_FILE | char * | Read options from the named option file instead of from my.cnf. |
MYSQL_READ_DEFAULT_GROUP | char * | Read options from the named group from my.cnf or the file specified with MYSQL_READ_DEFAULT_FILE. |
MYSQL_OPT_PROTOCOL | unsigned int * | Type of protocol to use. Should be one of the enum values of mysql_protocol_type defined in mysql.h. |
MYSQL_SHARED_MEMORY_BASE_NAME | char* | Named of of chared memory object for communication to server. Should be same as the option -shared-memory-base-name used for the mysqld server you want's to connect to. |
Note that the group client is always read if you use MYSQL_READ_DEFAULT_FILE or MYSQL_READ_DEFAULT_GROUP.
The specified group in the option file may contain the following options:
Option | Description |
connect-timeout | Connect timeout in seconds. On Linux this timeout is also used for waiting for the first answer from the server. |
compress | Use the compressed client/server protocol. |
database | Connect to this database if no database was specified in the connect command. |
debug | Debug options. |
disable-local-infile | Disable use of LOAD DATA LOCAL. |
host | Default hostname. |
init-command | Command to execute when connecting to MySQL server. Will automatically be re-executed when reconnecting. |
interactive-timeout | Same as specifying CLIENT_INTERACTIVE to mysql_real_connect(). See mysql_real_connect. |
local-infile[=(0|1)] | If no argument or argument != 0 then enable use of LOAD DATA LOCAL. |
max_allowed_packet | Max size of packet client can read from server. |
password | Default password. |
pipe | Use named pipes to connect to a MySQL server on NT. |
protocol=(TCP | SOCKET | PIPE | MEMORY) | Which protocol to use when connecting to server (New in 4.1) |
port | Default port number. |
return-found-rows | Tell mysql_info() to return found rows instead of updated rows when using UPDATE. |
shared-memory-base-name=name | Shared memory name to use to connect to server (default is "MySQL"). New in MySQL 4.1. |
socket | Default socket number. |
user | Default user. |
Note that timeout has been replaced by connect-timeout, but timeout will still work for a while.
For more information about option files, see Option files.
MYSQL mysql; mysql_init(&mysql); mysql_options(&mysql,MYSQL_OPT_COMPRESS,0); mysql_options(&mysql,MYSQL_READ_DEFAULT_GROUP,"odbc"); if (!mysql_real_connect(&mysql,"host","user","passwd","database",0,NULL,0)) { fprintf(stderr, "Failed to connect to database: Error: %s\n", mysql_error(&mysql)); }
The above requests the client to use the compressed client/server protocol and read the additional options from the odbc section in the my.cnf file.
Checks whether the connection to the server is working. If it has gone down, an automatic reconnection is attempted.
This function can be used by clients that remain idle for a long while, to check whether the server has closed the connection and reconnect if necessary.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Executes the SQL query pointed to by the null-terminated string query. The query must consist of a single SQL statement. You should not add a terminating semicolon (;) or \g to the statement.
mysql_query() cannot be used for queries that contain binary data; you should use mysql_real_query() instead. (Binary data may contain the \0 character, which mysql_query() interprets as the end of the query string.)
If you want to know if the query should return a result set or not, you can use mysql_field_count() to check for this. See mysql_field_count().
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
mysql_real_connect() attempts to establish a connection to a MySQL database engine running on host. mysql_real_connect() must complete successfully before you can execute any of the other API functions, with the exception of mysql_get_client_info().
The parameters are specified as follows:
The first parameter should be the address of an existing MYSQL structure. Before calling mysql_real_connect() you must call mysql_init() to initialize the MYSQL structure. You can change a lot of connect options with the mysql_options() call. See mysql_options().
The value of host may be either a hostname or an IP address. If host is NULL or the string "localhost", a connection to the local host is assumed. If the OS supports sockets (Unix) or named pipes (Windows), they are used instead of TCP/IP to connect to the server.
The user parameter contains the user's MySQL login ID. If user is NULL or the empty string "", the current user is assumed. Under Unix, this is the current login name. Under Windows ODBC, the current username must be specified explicitly. See ODBC administrator.
The passwd parameter contains the password for user. If passwd is NULL, only entries in the user table for the user that have a blank (empty) password field will be checked for a match. This allows the database administrator to set up the MySQL privilege system in such a way that users get different privileges depending on whether or not they have specified a password.
Note: Do not attempt to encrypt the password before calling mysql_real_connect(); password encryption is handled automatically by the client API.
db is the database name. If db is not NULL, the connection will set the default database to this value.
If port is not 0, the value will be used as the port number for the TCP/IP connection. Note that the host parameter determines the type of the connection.
If unix_socket is not NULL, the string specifies the socket or named pipe that should be used. Note that the host parameter determines the type of the connection.
The value of client_flag is usually 0, but can be set to a combination of the following flags in very special circumstances:
Flag name | Flag description |
CLIENT_COMPRESS | Use compression protocol. |
CLIENT_FOUND_ROWS | Return the number of found (matched) rows, not the number of affected rows. |
CLIENT_IGNORE_SPACE | Allow spaces after function names. Makes all functions names reserved words. |
CLIENT_INTERACTIVE | Allow interactive_timeout seconds (instead of wait_timeout seconds) of inactivity before closing the connection. The client's session wait_timeout variable will be set to the value of the session interactive_timeout variable. |
CLIENT_LOCAL_FILES | Enable LOAD DATA LOCAL handling. |
CLIENT_MULTI_STATEMENTS | Tell the server that the client may send multi-row-queries (separated with ;). If this flag is not set, multi-row-queries are disabled. New in 4.1. |
CLIENT_MULTI_RESULTS | Tell the server that the client can handle multiple-result sets from multi-queries or stored procedures. This is automatically set if CLIENT_MULTI_STATEMENTS is set. New in 4.1. |
CLIENT_NO_SCHEMA | Don't allow the db_name.tbl_name.col_name syntax. This is for ODBC. It causes the parser to generate an error if you use that syntax, which is useful for trapping bugs in some ODBC programs. |
CLIENT_ODBC | The client is an ODBC client. This changes mysqld to be more ODBC-friendly. |
CLIENT_SSL | Use SSL (encrypted protocol). This option should not be set by application programs; it is set internally in the client library. |
A MYSQL* connection handle if the connection was successful, NULL if the connection was unsuccessful. For a successful connection, the return value is the same as the value of the first parameter.
CR_CONN_HOST_ERROR | Failed to connect to the MySQL server. |
CR_CONNECTION_ERROR | Failed to connect to the local MySQL server. |
CR_IPSOCK_ERROR | Failed to create an IP socket. |
CR_OUT_OF_MEMORY | Out of memory. |
CR_SOCKET_CREATE_ERROR | Failed to create a Unix socket. |
CR_UNKNOWN_HOST | Failed to find the IP address for the hostname. |
CR_VERSION_ERROR | A protocol mismatch resulted from attempting to connect to a server with a client library that uses a different protocol version. This can happen if you use a very old client library to connect to a new server that wasn't started with the --old-protocol option. |
CR_NAMEDPIPEOPEN_ERROR | Failed to create a named pipe on Windows. |
CR_NAMEDPIPEWAIT_ERROR | Failed to wait for a named pipe on Windows. |
CR_NAMEDPIPESETSTATE_ERROR | Failed to get a pipe handler on Windows. |
CR_SERVER_LOST | If connect_timeout > 0 and it took longer than connect_timeout seconds to connect to the server or if the server died while executing the init-command. |
MYSQL mysql; mysql_init(&mysql); mysql_options(&mysql,MYSQL_READ_DEFAULT_GROUP,"your_prog_name"); if (!mysql_real_connect(&mysql,"host","user","passwd","database",0,NULL,0)) { fprintf(stderr, "Failed to connect to database: Error: %s\n", mysql_error(&mysql)); }
By using mysql_options() the MySQL library will read the [client] and [your_prog_name] sections in the my.cnf file which will ensure that your program will work, even if someone has set up MySQL in some non-standard way.
Note that upon connection, mysql_real_connect() sets the reconnect flag (part of the MYSQL structure) to a value of 1. This flag indicates, in the event that a query cannot be performed because of a lost connection, to try reconnecting to the server before giving up.
This function is used to create a legal SQL string that you can use in a SQL statement. See String syntax.
The string in from is encoded to an escaped SQL string, taking into account the current character set of the connection. The result is placed in to and a terminating null byte is appended. Characters encoded are NUL (ASCII 0), \n, \r, \, ', ", and Control-Z (see Literals). (Strictly speaking, MySQL requires only that backslash and the quote character used to quote the string in the query be escaped. This function quotes the other characters to make them easier to read in log files.)
The string pointed to by from must be length bytes long. You must allocate the to buffer to be at least length*2+1 bytes long. (In the worst case, each character may need to be encoded as using two bytes, and you need room for the terminating null byte.) When mysql_real_escape_string() returns, the contents of to will be a null-terminated string. The return value is the length of the encoded string, not including the terminating null character.
char query[1000],*end; end = strmov(query,"INSERT INTO test_table values("); *end++ = '\''; end += mysql_real_escape_string(&mysql, end,"What's this",11); *end++ = '\''; *end++ = ','; *end++ = '\''; end += mysql_real_escape_string(&mysql, end,"binary data: \0\r\n",16); *end++ = '\''; *end++ = ')'; if (mysql_real_query(&mysql,query,(unsigned int) (end - query))) { fprintf(stderr, "Failed to insert row, Error: %s\n", mysql_error(&mysql)); }
The strmov() function used in the example is included in the mysqlclient library and works like strcpy() but returns a pointer to the terminating null of the first parameter.
Executes the SQL query pointed to by query, which should be a string length bytes long. The query must consist of a single SQL statement. You should not add a terminating semicolon (;) or \g to the statement.
You must use mysql_real_query() rather than mysql_query() for queries that contain binary data, because binary data may contain the \0 character. In addition, mysql_real_query() is faster than mysql_query() because it does not call strlen() on the query string.
If you want to know if the query should return a result set or not, you can use mysql_field_count() to check for this. See mysql_field_count().
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Asks the MySQL server to reload the grant tables. The connected user must have the RELOAD privilege.
This function is deprecated. It is preferable to use mysql_query() to issue an SQL FLUSH PRIVILEGES statement instead.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Sets the row cursor to an arbitrary row in a query result set. The offset value is a row offset that should be a value returned from mysql_row_tell() or from mysql_row_seek(). This value is not a row number; if you want to seek to a row within a result set by number, use mysql_data_seek() instead.
This function requires that the result set structure contains the entire result of the query, so mysql_row_seek() may be used only in conjunction with mysql_store_result(), not with mysql_use_result().
The previous value of the row cursor. This value may be passed to a subsequent call to mysql_row_seek().
Returns the current position of the row cursor for the last mysql_fetch_row(). This value can be used as an argument to mysql_row_seek().
You should use mysql_row_tell() only after mysql_store_result(), not after mysql_use_result().
Causes the database specified by db to become the default (current) database on the connection specified by mysql. In subsequent queries, this database is the default for table references that do not include an explicit database specifier.
mysql_select_db() fails unless the connected user can be authenticated as having permission to use the database.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Enables or disables an option for the connection. option can have one of the following values:
MYSQL_OPTION_MULTI_STATEMENTS_ON | Enable multi statement support. |
MYSQL_OPTION_MULTI_STATEMENTS_OFF | Disable multi statement support. |
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
ER_UNKNOWN_COM_ERROR | The server didn't support mysql_set_server_option() (which is the case that the server is older than 4.1.1) or the server didn't support the option one tried to set. |
Asks the database server to shut down. The connected user must have SHUTDOWN privileges.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Returns a null-terminated string containing the SQLSTATE error code for the last error. The error code consists of five characters. '00000' means ``no error''. The values are specified by ANSI SQL and ODBC. For a list of possible values, see Error-returns.
Note that not all MySQL errors are yet mapped to SQLSTATE's. The value 'HY000' (general error) is used for unmapped errors.
This function was added to MySQL 4.1.1.
See mysql_errno(). See mysql_error(). See mysql_stmt_sqlstate.
mysql_ssl_set() is used for establishing secure connections using SSL. It must be called before mysql_real_connect().
mysql_ssl_set() does nothing unless OpenSSL support is enabled in the client library.
mysql is the connection handler returned from mysql_init(). The other parameters are specified as follows:
key is the pathname to the key file.
cert is the pathname to the certificate file.
ca is the pathname to the certificate authority file.
capath is the pathname to a directory that contains trusted SSL CA certificates in pem format.
cipher is a list of allowable ciphers to use for SSL encryption.
Any unused SSL parameters may be given as NULL.
This function always returns 0. If SSL setup is incorrect, mysql_real_connect() will return an error when you attempt to connect.
Returns a character string containing information similar to that provided by the mysqladmin status command. This includes uptime in seconds and the number of running threads, questions, reloads, and open tables.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
You must call mysql_store_result() or mysql_use_result() for every query that successfully retrieves data (SELECT, SHOW, DESCRIBE, EXPLAIN).
You don't have to call mysql_store_result() or mysql_use_result() for other queries, but it will not do any harm or cause any notable performance if you call mysql_store_result() in all cases. You can detect if the query didn't have a result set by checking if mysql_store_result() returns 0 (more about this later one).
If you want to know if the query should return a result set or not, you can use mysql_field_count() to check for this. See mysql_field_count().
mysql_store_result() reads the entire result of a query to the client, allocates a MYSQL_RES structure, and places the result into this structure.
mysql_store_result() returns a null pointer if the query didn't return a result set (if the query was, for example, an INSERT statement).
mysql_store_result() also returns a null pointer if reading of the result set failed. You can check if an error occurred by checking if mysql_error() returns a non-empty string, if mysql_errno() returns non-zero, or if mysql_field_count() returns zero.
An empty result set is returned if there are no rows returned. (An empty result set differs from a null pointer as a return value.)
Once you have called mysql_store_result() and got a result back that isn't a null pointer, you may call mysql_num_rows() to find out how many rows are in the result set.
You can call mysql_fetch_row() to fetch rows from the result set, or mysql_row_seek() and mysql_row_tell() to obtain or set the current row position within the result set.
You must call mysql_free_result() once you are done with the result set.
mysql_store_result() resets mysql_error and mysql_errno if it succeeds.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_OUT_OF_MEMORY | Out of memory. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Returns the thread ID of the current connection. This value can be used as an argument to mysql_kill() to kill the thread.
If the connection is lost and you reconnect with mysql_ping(), the thread ID will change. This means you should not get the thread ID and store it for later. You should get it when you need it.
You must call mysql_store_result() or mysql_use_result() for every query that successfully retrieves data (SELECT, SHOW, DESCRIBE, EXPLAIN).
mysql_use_result() initiates a result set retrieval but does not actually read the result set into the client like mysql_store_result() does. Instead, each row must be retrieved individually by making calls to mysql_fetch_row(). This reads the result of a query directly from the server without storing it in a temporary table or local buffer, which is somewhat faster and uses much less memory than mysql_store_result(). The client will only allocate memory for the current row and a communication buffer that may grow up to max_allowed_packet bytes.
On the other hand, you shouldn't use mysql_use_result() if you are doing a lot of processing for each row on the client side, or if the output is sent to a screen on which the user may type a ^S (stop scroll). This will tie up the server and prevent other threads from updating any tables from which the data is being fetched.
When using mysql_use_result(), you must execute mysql_fetch_row() until a NULL value is returned, otherwise, the unfetched rows will be returned as part of the result set for your next query. The C API will give the error Commands out of sync; you can't run this command now if you forget to do this!
You may not use mysql_data_seek(), mysql_row_seek(), mysql_row_tell(), mysql_num_rows(), or mysql_affected_rows() with a result returned from mysql_use_result(), nor may you issue other queries until the mysql_use_result() has finished. (However, after you have fetched all the rows, mysql_num_rows() will accurately return the number of rows fetched.)
You must call mysql_free_result() once you are done with the result set.
mysql_use_result() resets mysql_error and mysql_errno if it succeeds.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. |
CR_OUT_OF_MEMORY | Out of memory. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
Returns the number of warnings generated during execution of the previous SQL statement. Available from MySQL 4.1.
Returns true if more results exist from the currently executed query, and the application must call mysql_next_result() to fetch the results. Available from MySQL 4.1.
TRUE (1) if more results exist. FALSE (0) if no more results exist.
Note that in most cases one instead call mysql_next_result() to test if more result exists and initiate the next result set if it existed.
See C API multiple queries. See mysql_next_result.
If more query results exist, mysql_next_result() reads the next query results and returns the status back to application. Available from MySQL 4.1.
Note that you must call mysql_free_result() for the preceding query if it returned a result set.
After calling mysql_next_result() the state of the connection is as if you had called mysql_real_query() for the next query. This means that you can now call mysql_store_result(), mysql_warning_count(), mysql_affected_rows() ... on the connection.
If mysql_next_result() returns an error, no other statements will be executed and there is no more results to fetch.
0 if successful and there was more results -1 if no more results > 0 if an error occurred.
CR_COMMANDS_OUT_OF_SYNC | Commands were executed in an improper order. For example if you didn't call mysql_use_result() for a previous result set. |
CR_SERVER_GONE_ERROR | The MySQL server has gone away. |
CR_SERVER_LOST | The connection to the server was lost during the query. |
CR_UNKNOWN_ERROR | An unknown error occurred. |
my_bool mysql_change_user(MYSQL *mysql, const char *user, const char *password, const char *db)
MYSQL *mysql_connect(MYSQL *mysql, const char *host, const char *user, const char *passwd)
You should use mysql_real_escape_string() instead!
This function is identical to mysql_real_escape_string() except that mysql_real_escape_string() takes a connection handler as its first argument and escapes the string according to the current character set. mysql_escape_string() does not take a connection argument and does not respect the current charset setting.
MYSQL_FIELD *mysql_fetch_field_direct(MYSQL_RES *result, unsigned int fieldnr)
unsigned int mysql_field_count(MYSQL *mysql)
If you are using a version of MySQL earlier than Version 3.22.24, you should use unsigned int mysql_num_fields(MYSQL *mysql) instead.
MYSQL_FIELD_OFFSET mysql_field_seek(MYSQL_RES *result, MYSQL_FIELD_OFFSET offset)
unsigned int mysql_num_fields(MYSQL_RES *result)
or:
unsigned int mysql_num_fields(MYSQL *mysql)
The second form doesn't work on MySQL Version 3.22.24 or newer. To pass a MYSQL* argument, you must use unsigned int mysql_field_count(MYSQL *mysql) instead.
MYSQL *mysql_real_connect(MYSQL *mysql, const char *host, const char *user, const char *passwd, const char *db, unsigned int port, const char *unix_socket, unsigned long client_flag)
unsigned long mysql_real_escape_string(MYSQL *mysql, char *to, const char *from, unsigned long length)
int mysql_set_server_option(MYSQL *mysql, enum enum_mysql_set_option option)
int mysql_ssl_set(MYSQL *mysql, const char *key, const char *cert, const char *ca, const char *capath, const char *cipher)