通过外连接提高SQL性能(2)

来源：未知责任编辑：责任编辑发表时间:2014-02-02 17:50　点击:次

select a.CID from

v_contents a,

(select distinct b.fieldvalue from v_contentdatavisual_zh b, v_contents c

where c.type=1 and c.updateflg!='2' and b.cid=c.cid and b.fieldid like 'download_onlineServiceID'

and b.fieldvalue is not null) b

where a.cid=b.fieldvalue(+) and b.fieldvalue is null

and

a.spid like '%' and a.type=98 and a.updateflg = '0' and a.curstatus='5'

修改之后的执行计划如下：

SQL> @?/rdbms/admin/utlxpls

PLAN_TABLE_OUTPUT

--------------------------------------------------------------------------

tes | Cost |

------------------------------------------------------------------------------

| 0 | SELECT STATEMENT | | |

PLAN_TABLE_OUTPUT

--------------------------------------------------------------------------------

| |

| 1 | FILTER | | |

| |

| 2 | MERGE JOIN OUTER | | |

| |

| 3 | SORT JOIN | | |

| |

PLAN_TABLE_OUTPUT

--------------------------------------------------------------------------------

| |

| 5 | SORT JOIN | | |

| |