April 2008
Intermediate to advanced
566 pages
21h 55m
English
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Name
ENUM
Synopsis
ENUM('value', ...) [CHARACTER SET character_set] [COLLATE collation]An ENUM column is one in which all possible choices are enumerated
(e.g., ENUM('yes', 'no', 'maybe')). It’s possible
for it to contain a blank value (i.e., '') and NULL. If an
ENUM column is set up to allow NULL values, NULL
will be the default value. If an ENUM column is set
up with NOT NULL, NULL isn’t allowed and the
default value becomes the first element given.
MySQL stores a numeric index of the enumerated values in the
column, 1 being the first value. The values can be retrieved when the
column is used in a numeric context (e.g., SELECT col1 + 0
FROM table1;). The reverse may be performed when entering
data into a column (e.g., UPDATE table1 SET col1 =
3; to set the value to the third element). The column values
are sorted in ascending order based on the numeric index, not on their
corresponding enumerated values. If you want to use a character set
for the column other than the default for the table, you can give one
for the column. Values are sorted based on the collation of the
character set for the column.
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