一道行列转换的sql

有report表：它里面 id  name   state    customerid 四个字段，id为主键 ，customerid为外键
state 0， 1，2   //  未使用  更新  删除

根据customerid写一条sql （注意是一条）生成表的结构如下：

customerid  state0   state1  state2
001          11       212      333
002          15       545      3


答案如下：

典型的行转列问题



select distinct r.customerid,
(select count(r0.id) from report r0 where r.customerid = customerid and r0.state = 0) state0,
(select count(r1.id) from report r1 where r.customerid = customerid and r1.state = 1) state1,
(select count(r2.id) from report r2 where r.customerid = customerid and r2.state = 2) state2
from report r