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1.9.6.3. ENUM and SET Constraints

ENUM and SET columns provide an efficient way to define columns that can contain only a given set of values. See Section 10.4.4, “The ENUM Type”, and Section 10.4.5, “The SET Type”. However, in MySQL 4.1 and earlier, ENUM and SET columns do not provide true constraints on entry of invalid data:

  • ENUM columns always have a default value. If you specify no default value, then it is NULL for columns that can have NULL, otherwise it is the first enumeration value in the column definition.

  • If you insert an incorrect value into an ENUM column or if you force a value into an ENUM column with IGNORE, it is set to the reserved enumeration value of 0, which is displayed as an empty string in string context.

  • If you insert an incorrect value into a SET column, the incorrect value is ignored. For example, if the column can contain the values 'a', 'b', and 'c', an attempt to assign 'a,x,b,y' results in a value of 'a,b'.


User Comments

Posted by flobee (c) on November 6 2005 7:09pm[Delete] [Edit]

like already metioned: "An ENUM value must be one of those listed ..."
when fetching enum fields eg. to an array:
enum('a','b','c') == array(1=>'a', 2=>'b', 3=>'c')

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