create table abc(A int,B int)
Select A,count(B) as total from ABC group by A Select A,count(B) as total1 from ABC where B > 30 group by A Select A,count(B) as totlal2 from ABC where B > 20 group by A
如何合并这三个查询？
得到一个查询结果：
A,total,total1,total2
答：
Select A, count(B) as total, sum(case when B > 30 then 1 else 0 end) as total1, sum(case when B > 20 then 1 else 0 end) as total2 from ABC group by A
原文：http://www.cnblogs.com/xiao-momo/p/5810335.html