The ENUM Type

An ENUM is a string object whose value normally is chosen from a list of allowed values that are enumerated explicitly in the column specification at table creation time.

The value may also be the empty string ("") or NULL under certain circumstances:

Each enumeration value has an index:

For example, a column specified as ENUM("one", "two", "three") can have any of the values shown here. The index of each value is also shown:

ValueIndex
NULLNULL
""0
"one"1
"two"2
"three"3

An enumeration can have a maximum of 65535 elements.

Starting from 3.23.51 trailing spaces are automatically deleted from ENUM values when the table is created.

Lettercase is irrelevant when you assign values to an ENUM column. However, values retrieved from the column later have lettercase matching the values that were used to specify the allowable values at table creation time.

If you retrieve an ENUM in a numeric context, the column value's index is returned. For example, you can retrieve numeric values from an ENUM column like this:

mysql> SELECT enum_col+0 FROM tbl_name;

If you store a number into an ENUM, the number is treated as an index, and the value stored is the enumeration member with that index. (However, this will not work with LOAD DATA, which treats all input as strings.) It's not advisable to store numbers in an ENUM string because it will make things confusing.

ENUM values are sorted according to the order in which the enumeration members were listed in the column specification. (In other words, ENUM values are sorted according to their index numbers.) For example, "a" sorts before "b" for ENUM("a", "b"), but "b" sorts before "a" for ENUM("b", "a"). The empty string sorts before non-empty strings, and NULL values sort before all other enumeration values. To prevent unexpected results, specify the ENUM list in alphabetical order. You can also use GROUP BY CONCAT(col) to make sure the column is sorted alphabetically rather than by index number.

If you want to get all possible values for an ENUM column, you should use: SHOW COLUMNS FROM table_name LIKE enum_column_name and parse the ENUM definition in the second column.