1、业务场景：
有些需求需要对多个表分别统计出结果，然后使用每个表统计的结果进行汇总，这个时候临时表就发挥作用了。
2、简单使用：
with t1 as(select empId,yearMonth,sum(salary) as'a'from tb_salary where yearMonth = '-01'group by empId,yearMonth),t2 as (select empId,yearMonth,sum(salary) as'a'from tb_salary where yearMonth = '-02'group by empId,yearMonth ),t as (select t1.empId e1, t2.empId e2, t1.empId e3, isnull(t1.yearMonth,'-01') m1,isnull(t2.yearMonth,'-02') m2, '与上月差额' m3 ,isnull(t1.a,'0') a1, isnull(t2.a,'0') a2,emp.staffNo,emp.staffName,Pathfrom t1 right join t2 on t1.empId = t2.empId RIGHT JOIN tb_employees emp on t2.empId = emp.empId) -- 行转列select 1 n,tt.e2,tt.staffNo,tt.m1,tt.a1 from (select * from from t) tt union allselect 2 n,tt.e2,tt.staffNo,tt.m2,tt.a2 from (select * from from t) tt union allselect 3 n,tt.e2,tt.staffNo,tt.m3,(tt.a2-tt.a1) a3 from (select * from from t where t.staffNo = '4289') ttORDER BY t.e2 desc,n asc;
