MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
ENUM and
SET columns provide an
efficient way to define columns that can contain only a given
set of values. See Section 13.3.5, “The ENUM Type”, and
Section 13.3.6, “The SET Type”.
Unless strict mode is disabled (not recommended, but see
Section 7.1.11, “Server SQL Modes”), the definition of a
ENUM or
SET column acts as a constraint
on values entered into the column. An error occurs for values
that do not satisfy these conditions:
An
ENUMvalue must be one of those listed in the column definition, or the internal numeric equivalent thereof. The value cannot be the error value (that is, 0 or the empty string). For a column defined asENUM('a','b','c'), values such as'','d', or'ax'are invalid and are rejected.A
SETvalue must be the empty string or a value consisting only of the values listed in the column definition separated by commas. For a column defined asSET('a','b','c'), values such as'd'or'a,b,c,d'are invalid and are rejected.
Errors for invalid values can be suppressed in strict mode if
you use INSERT
IGNORE or UPDATE IGNORE. In this
case, a warning is generated rather than an error. For
ENUM, the value is inserted as
the error member (0). For
SET, the value is inserted as
given except that any invalid substrings are deleted. For
example, 'a,x,b,y' results in a value of
'a,b'.