in和exist的主要区别体现在对sql执行计划的影响上。传统上认为，如果子查询的条件更具选择性（selective），就用in；而如果父查询（外层查询）的条件更具选择性（selective），就用exist。具体的内容可以参考以下oracle原厂的手册，不好意思，oracle的原厂手册都是英文版的。另外需要特别注意的是，in和exis...
This allows the selective predicates in the pare nt query to be applied before fil 24、ter ing the rows aga inst the EXISTS criteria.所以以后大家遇到有类型的情况,优化使用not exist ,毕竟是在所有 oracle版本中通用的。我们再来看个对not in优化的思路:首先来看两个sql,返回结果相同,但是耗时差别很大:...
It always resultsinafullscanofT1 whereas the first query can makeuseofanindexonT1(x). 但是,不要忘了,上面的还是在RBO下做的,RBO现在已经是历史了,所以我们要在CBO下再测试一次。 下面这一段是in 模式 SQL>altersessionsetoptimizer_mode='ALL_ROWS'; Session altered. SQL>select/*+ gather_plan_statisti...
for x in ( select * from t1 ) loop if ( exists ( select null from t2 where y = x.x ) then OUTPUT THE RECORD end if end loop It always results in a full scan of T1 whereas the first query can make use of an index on T1(x). So, when is where exists appropriate and in ap...
通过使用 exists,Oracle 会首先检查主查询,然后运行子查询直到它找到第一个匹配项,这就节省了时间。 Oracle 在执行IN子查询时,首先执行子查询,并将获得的结果列表存放在一个加了索引的临时表中。在 执行子查询乊前,系统先将主查询挂起,待子查询执行完毕,存放在临时表中以后再执行主查询。这也就 ...
以下是 Oracle官方的解释: In certain circumstances, itis better to use IN rather than EXISTS. In gene ral, itf he selective predicate isin the subqu ery, thenuse IN. If theselective predicate is inth e parent query, ht en use EXISTS. Som etimes, Oracle can rewrite a subquer y when ...
Method Summary Methods inherited from interface oracle.bpel.services.workflow.query.model.CountViewTasksRequestType getExtraPredicate, getViewId, getWorkflowContext, setExtraPredicate, setViewId, setWorkflowContextSkip navigation links Overview Package Class Tree Deprecated Index Help Oracle ...
INSERT INTO Terminal (ID, type_ID, Name,IP_address,tags,create_access_ID,Status_ID) VALUES (`Id`, `type_ID`,`anshu`,`10.40.192.88`,`Registery`,`a59660306a0e1e`,`0`); ABOVE QUERY NOT WORKING IN MYSQL 8.0 FOLLOWING ERROR OCCURRED ...
at oracle.jdbc.driver.OraclePreparedStatementWrapper.executeQuery(OraclePreparedStatementWrapper.java:1493) at weblogic.jdbc.wrapper.PreparedStatement.executeQuery(PreparedStatement.java:135) at glog.util.jdbc.noserver.SqlQuery.executeQuery(SqlQuery.java:164) ...
Methods inherited from class oracle.toplink.sdk.AbstractSDKCall addReadTranslation, addReadTranslations, addReadTranslations, addWriteTranslation, addWriteTranslations, addWriteTranslations, buildDefaultTranslator, buildNewQueryMechanism, buildQueryMechanism, clone, clone, getFieldTranslator, getLogString, is...