mysql sum null תΪ0
MySQLۺϺsumΪʱôֵΪ0 - ٶȾ
1 һmysqlĿͻ ʹnavicatݿ 2 ڶѯһʹþۺϺѯijһУ...
mysql sumֵʱnullô
IFNULL(ֵֶ,0) ķΪNULLֵΪ0ȻӡʾSELECT SUM(IFNULL(ֵֶ,0) )...
ѯsql ,ΪnullתΪ0ô
update TABLE set ֶ=0 where isnull(ֶ)ֶΪʵֶTABLEΪʵʱ
ΪʲôMYSQL SUM õĽ0?
¥ʹڼ˵ţȥŻõȷģſԡ
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NULLΪδֵǸֵֵΪաMysqlAccess ӦƵġNull ַ,...
SQLйNULLֵ?
Ϊcust_idΪnullˣôһݻϾ൱ڲˣûһûʲô̫
mysql ݿַɾ滻⡣Ҫɾ滻...
5ʱnullתΪ0IJѯ select m.*,v.*,ifnull(v.l_addtime,0) as vtime from members m ...
PostgreSQL MySQL ,ƺ?
NOT NULLָʾijвܴ洢 NULL ֵUNIQUEȷijеֵΨһġ'PRIMARY KeyNOT NULL ...
һ SQL Ӳѯ - ܺ
not distinct joinӦmysql<=>,null<=>nullĽΪtrue,ǿjoinһ...