假设WITH AS中的语句仅仅被调用一次的话,不妨不要使用HINTMATERIALIZE。由于使用HINTMATERIALIZE第一次查询会创建基于视图结果的暂时表,这也耗费一些时间。 多次使用的话能够使用HINTMATERIALIZE。
加materialize hint,强制oracle生成临时表SQL>withtas(select/*+ materialize */t1.*fromtest1 t1,test2 t2wheret1.object_id=t2.object_id)select*fromt,test3 t3wheret.object_id=t3.object_id;11rowsselected.ExecutionPlan---Planhashvalue:3288461629---|Id...
最后的结果还一样,后来想到WITH AS能提高SQL的查询速度,就把影响SQL运行的那段SQL放到WITH AS里面,结果还是一样。后来尝试把HINTMATERIALIZE和WITH AS结合使用,改动成例如以下的SQL,查询速度马上提升了非常多。例如以下图所看到的。运行计划中FILTER的NOT EXISTS不存在了。 WITHPARAMSAS(SELECT''USER_ID,''SDATE,'%...
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Note the use of theOracleundocumented “materialize” hint in the “WITHclause”. TheOraclematerialize hint is used to ensure that theOraclecost-based optimizer materializes the temporary tables that are created inside the “WITH” clause. This is not necessary in Oracle10g, but it helps ensure...
sales_by_store AS select store_name, sum(quantity) store_sales from store natural join sales SELECT store_name FROM store, sum_sales, number_stores, sales_by_store where store_sales > (all_sales / nbr_stores) ; Note the use of the Oracle undocumented “materialize” hint in the “WITH...
The Oracle materialize hint is used to ensure that the Oracle cost-based optimizer materializes the temporary tables that are created inside the “WITH” clause. This is not necessary in Oracle10g, but it helps ensure that the tables are only created one time....
with temp as (select /*+hint1*/ ***)select /*+hint2*/* from temp;--hint1作用于temp内结果集，hint2作用域temp外
withaas(select*fromtest) select*froma; 其实就是把一大堆重复用到的SQL语句放在withas里面,取一个别名,后面的查询就可以用它 这样对于大批量的SQL语句起到一个优化的作用,而且清楚明了 下面是搜索到的英文文档资料 AboutOracleWITHclause StartinginOracle9irelease2weseeanincorporationoftheSQL-99“WITHclause”,...
同一个用户下执行一样的语句如果大小写不一样或加了hint的话则会出现多个V$SQL记录,说明V$SQL对应的sql语句必须一模一样,如果alter system flush shared_pool(主站慎用)后再执行一样的语句,发现语句在V$SQL中的SQL_ID和HASH_VALUE与之前的一样,说明SQL_ID和HASH_VALUE应该是oracle自己的一套算法来的,只是根据...