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


MySQLgroup by ,ܷcountԪؽɸѡ...

7.SUM()һֵֵֶֻܺܽ͡Σзǿֵͣûֵ򷵻...


mysql varchar Ĭֵ null Ϳ ...

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...