我有以下查询:类似的查询有这样不同的执行时间
SELECT nvl(sum(adjust1),0)
FROM (
SELECT
ManyOperationsOnFieldX adjust1,
a, b, c, d, e
FROM (
SELECT
a, b, c, d, e,
SubStr(balance, INSTR(balance, '[&&2~', 1, 1)) X
FROM
table
WHERE
a >= To_Date('&&1','YYYYMMDD')
AND a < To_Date('&&1','YYYYMMDD')+1
)
)
WHERE
b LIKE ...
AND e IS NULL
AND adjust1>0
AND (b NOT IN ('...','...','...'))
OR (b = '... AND c <> NULL)
我试图把它改成这样:
SELECT nvl(sum(adjust1),0)
FROM (
SELECT
ManyOperationsOnFieldX adjust1
FROM (
SELECT
SubStr(balance, INSTR(balance, '[&&2~', 1, 1)) X
FROM
table
WHERE
a >= To_Date('&&1','YYYYMMDD')
AND a < To_Date('&&1','YYYYMMDD')+1
AND b LIKE '..'
AND e IS NULL
AND (b NOT IN ('..','..','..'))
OR (b='..' AND c <> NULL)
)
)
WHERE
adjust1>0
米的意图是在最内层查询所有过滤,并且只给外面的那个我必须经营很多的领域X.然而,firts(原始)查询需要几秒钟才能执行,而第二个查询甚至不会完成。我等了将近20分钟,仍然没有得到答案。
是否有明显的原因会发生这种情况,我可能会忽略?
这些是他们每个人的计划:
SELECT STATEMENT optimizer=all_rows (cost = 973 Card = 1 bytes = 288)
SORT (aggregate)
PARTITION RANGE (single) (cost=973 Card = 3 bytes = 864)
TABLE ACCESS (full) OF "table" #3 TABLE Optimizer = analyzed(cost=973 Card = 3 bytes=564)
SELECT STATEMENT optimizer=all_rows (cost = 750.354 Card = 1 bytes = 288)
SORT (aggregate)
PARTITION RANGE (ALL) (cost=759.354 Cart = 64.339 bytes = 18.529.632)
TABLE ACCESS (full) OF "table" #3 TABLE Optimizer = analyzed(cost=750.354 Card = 64.339 bytes=18.529.632)
每个查询的解释计划是什么? – Ollie 2012-07-19 14:51:42
第二个SQL中有一个语法错误 - adjust1(第一个SQL在第二个SQL中缺少的下一行上有一个列表“a,b,...”)后的逗号逗号。 – 2012-07-19 14:53:02
该计划显示您的第二个查询正在扫描您桌面上的所有分区,而第一个只扫描一个分区,因此速度更快。看看两次扫描之间的成本差异。 – Ollie 2012-07-19 15:00:11