摘要： select *from (SELECT @num:=0,@AAA:= 0) temp join( select @num := if(@AAA = AAA, @num + 1, 1) as row_number, @AAA := AAA as Dummy, mt.* from table1 mt where Created_Time BETWEEN DATE_SU... 阅读全文

摘要： alter table table1 add (F1 CHAR(1) default 'O'); -- 如果是大表, 很耗时, 会将之前的数据此字段全部赋值 ==>alter table table1 add (F1 CHAR(1)); alter table table1 modify F1 default 'O'; 阅读全文