----- Original Message ----- From: pascal barbedor To: [EMAIL PROTECTED] Sent: Sunday, March 31, 2002 6:19 AM Subject: sum() autoconvert null to zero
Egor, >Null is an unidentified value, but MySQL will store 0 or ''. You can read about >it at: > http://www.mysql.com/doc/B/u/Bugs.html hi thanks for answer, but the page you mention only talk about converting null to zero if null value not allowed in a column : If you try to store NULL into a column that doesn't take NULL values, MySQL Server will store 0 or '' (empty string) in it instead. (This behavior can, however, be changed with the -DDONT_USE_DEFAULT_FIELDS compile option). in my case, null values ARE allowed in the column, but if i sum(col), it will be as if null values converted to zero. for instance : create table t (N short null, G char(1)) insert into t values (2,'a') insert into t values (3,'a') insert into t values (null,'b') resul in: field N G row 1 2 a row 2 3 a row 3 null b and then select sum(N) from t gives 5, instead of null. and select sum(N), G from t group by G gives a 5 b 0 instead of a 5 b null as expected. thanks --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
