SQL Tuning 基础概述02 - Explain plan的使用
SQL Tuning 基础概述02 - Explain plan的使用
1.explain plan的使用
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SQL>
explain plan for delete from t_jingyu;Explained.SQL> select * from table(dbms_xplan.display);PLAN_TABLE_OUTPUT--------------------------------------------------------------------------------------------------------------------------------------------Plan
hash value: 1368587462-----------------------------------------------------------------------|
Id | Operation | Name | Rows |
Cost (%CPU)| Time |-----------------------------------------------------------------------|
0 | DELETE STATEMENT
| | 1864K| 978 (2)| 00:00:12 ||
1 | DELETE |
T_JINGYU | | | ||
2 | TABLE ACCESS FULL|
T_JINGYU | 1864K| 978 (2)| 00:00:12 |-----------------------------------------------------------------------Note----- - dynamic sampling
used for this
statement (level=2)13 rows selected |
2.explain plan 只是显示执行计划，并不会真正执行delete语句·
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SQL> select count(*) from t_jingyu; COUNT(*)---------- 2097152 |
