|List:||General Discussion||« Previous MessageNext Message »|
|From:||Jigal van Hemert||Date:||April 26 2005 12:41pm|
|Subject:||why NOT NULL in PRIMARY key??|
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http://dev.mysql.com/doc/mysql/en/silent-column-changes.html mentions that "Columns that are part of a PRIMARY KEY are made NOT NULL even if not declared that way. " And http://dev.mysql.com/doc/mysql/en/create-table.html tells me that "A PRIMARY KEY is a unique KEY where all key columns must be defined as NOT NULL. If they are not explicitly declared as NOT NULL, MySQL declares them so implicitly (and silently). " Why is this? I actually do need NULL values (they really are not equal to '0', etc.), but also need this column as part of the PRIMARY key in an InnoDB table... It can't have anything to do with the 'uniqueness' of the data, since I can have a lot of 'zero'-values in the column, as long as the combination of columns in the PRIMARY key results in unique values. Regards, Jigal.