内容摘要：本文结合笔者实际的工作情况，说明了如何使用with as改写存储过程，从而大幅提高SQL的运行时间……
)
GROUP BY sku;
我们来看该SQL所花费的时间为：
SQL> set timing on
SQL> /
。。。。。。。。。。。。。。。。。。。。。。。。。。。。。
SKU INITQTY INQTY OUTQTY LASTQTY
-------- ---------- ---------- ---------- ----------
00106162 0 0 12 60
00106467 0 20 10 60
已选择956行。
已用时间: 00: 00: 19.08
然后，我们来对该SQL进行改写一番，如下所示：
WITH result AS (
SELECT /*+ materialize */ day,sku,inqty,outqty,lastqty
FROM fin
WHERE day>=to_date('20030713','yyyymmdd') AND day<=to_date('20030714','yyyymmdd'))
SELECT
sku,
sum(initqty) as initqty,
sum(inqty) as inqty,
sum(outqty) as outqty,
sum(lastqty) as lastqty
FROM (
SELECT sku,lastqty as initqty,0 as inqty,0 as outqty,0 as lastqty
FROM result
WHERE day=to_date('20030713','yyyymmdd')
UNION ALL
SELECT sku,0 as initqty,inqty,outqty,0 as lastqty
FROM result
WHERE day=to_date('20030714','yyyymmdd')
UNION ALL
SELECT sku,0 as initqty,0 as inqty,0 as outqty,lastqty
FROM result
WHERE day=to_date('20030714','yyyymmdd')
)
GROUP BY sku;
我们来看修改后的SQL所花费的时间为：
SQL> set timing on
SQL> /
。。。。。。。。。。。。。。。。。。。。。。。。。。。。。
SKU INITQTY INQTY OUTQTY LASTQTY
-------- ---------- ---------- ---------- ----------
00106162 0 0 12 60
00106467 0 20 10 60
已选择956行。
已用时间: 00: 00: 06.06
从这里可以看到，通过WITH AS可以从20秒降低到6秒，几乎提高了65%的性能。
来源：IT168 作者：hanson 责编：豆豆技术应用