摘:case用法

create table #(id int,vote int)

insert into # values(44,-2)

insert into # values(51,-3)

insert into # values(51,1)

insert into # values(52,-1)



select id,max(case  when vote<0 then vote else null end) as '-vote',max(case  when vote>0 then vote else null end) as '+vote' from # group by id

id          -vote       +vote
----------- ----------- -----------
44          -2          NULL
51          -3          1
52          -1          NULL
警告: 聚合或其他 SET 操作消除了空值。

(3 行受影响)