mysql - 用户变量不递增

Question

为什么以下查询不会增加 seq？

    SELECT   @sq :=if(@previous=uid,@sq,0)+1 as seq
            ,@previous:=uid as user
    FROM test

结果：

seq    user
1      111
1      111
1      111
1      222
1      222
1      222

Answer 1

你忘了set @sq:=0,@previous:=0在前面做什么？

或者，您始终可以将其加入查询：

SELECT   @sq :=if(@previous=uid,@sq,0)+1 as seq
        ,@previous:=uid as user
FROM test, (select @sq:=0, @previous:=0) foo