Introduced in 7.3 and requires V733_PLANS_ENABLED=TRUE and CBO, may be hinted using INDEX_FFS hint, uses multiblock i/o, can be executed in parallel, can be used to access second column of concatenated indexes. This is because we are selecting all of the index. ...
Oracle Database generates an internal SQL statement, which in turn generates a recursive call.In short, recursive calls are basically SQL performed on behalf of your SQL.So, if you had to parse the query, for example, you might have had to run some other queries to get data...
多表连接的三种方式详解 HASH JOIN MERGE JOIN NESTED LOOP 对于子查询,它的Cardinality将决定子查询是使用索引还是使用全表扫描的方式访问数据。 三. SQL 的执行计划 生成SQL的执行计划是Oracle在对SQL做硬解析时的一个非常重要的步骤,它制定出一个方案告诉Oracle在执行这条SQL时以什么样的方式访问数据:索引还是全...
Introduced in 7.3 and requires V733_PLANS_ENABLED=TRUE and CBO, may be hinted using INDEX_FFS hint, uses multiblock i/o, can be executed in parallel, can be used to access second column of concatenated indexes. This is because we are selecting all of the index. ...
Oracle 10g的执行计划,关键字换成了rows: 执行计划 --- Plan hash value: 2137789089 --- | Id | Operation | Name |Rows| Bytes | Cost (%CPU)| Time | ---
Plan hash value: 3458767806 --- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --- | 0 | SELECT STATEMENT | | 8 | 64 | 2 (0)| 00:00:01 | | 1 | TABLE ACCESS FULL| DAVE | 8 | 64 |
Plan hash value: 3458767806 --- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --- | 0 | SELECT STATEMENT | | 8 | 64 | 2 (0)|
Oracle 数据库中的(Explain Plan)知识 备注:此博客为转载,方便自己学习Oracle数据库,作者Dave翻译的书:【Oracle数据库问题<解决方案和故障排除手册>】如果要分析某条SQL的性能问题,通常我们要先看SQL的执行计划,看看SQL的每一步执行是否存在问题。 如果一条SQL平时执行的好好的,却有一天突然性能很差,如果排除了系统...
Oracle 10g的执行计划,关键字换成了rows: 执行计划 --- Plan hash value: 2137789089 --- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ---
plan_hash_valuefromdba_hist_sqlstat a, dba_hist_snapshot bwherea.snap_id=b.snap_idandsql_id='089dbukv1aanh'orderby2,1 Step3. 如果最近发生解析计划变更,并导致效率变慢,通过SPM绑定之前的解析计划 (脚本coe_xfr_sql_baseline.sql) SQL>@D:\Gavin\coe_xfr_sql_baseline.sql ...