內聯視圖、標量子查詢、WITH子查詢分解的示例

內聯視圖、標量子查詢、WITH子查詢分解的示例
-- 內聯視圖 （子查詢在from後面，作爲一個表）
select p.pname,c1_sum1,c2_sum2
from p,
(select id,sum(q1) c1_sum1 from s1 group by id) s1,
(select id,sum(q2) c2_sum2 from s2 group by id) s2
where p.id=s1.id
and p.id=s2.id

-- 標量子查詢（子查詢在select後面，作爲一個字段，可與表關聯）
select 
p.pname,
(select sum(q1) c1_sum1 from s1 where s1.id=p.id) c1_sum1,
(select sum(q2) c1_sum1 from s2 where s2.id=p.id) c2_sum2
from p

-- with子查詢分解（先定義子查詢作爲一個變量，再使用）
with c1_vw as (select id,sum(q1) sum1 from s1 group by id),
c2_vw as (select id,sum(q2) sum2 from s2 group by id),
c1_c2 as (select t1.id,t1.sum1,t2.sum2 from c1_vw t1,c2_vw t2 where t1.id=t2.id)
select p.pname,sum1,sum2
from p,c1_c2
where p.id=c1_c2.id