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ORACLESQL性能优化系列(十一)
作者:武汉SEO闵涛  文章来源:敏韬网  点击数2679  更新时间:2009/4/22 23:22:13  文章录入:mintao  责任编辑:mintao
      63749  bytes sent via SQL*Net to client

       7751  bytes received via SQL*Net from client

         68  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

       1003  rows processed

SQL> select * from unionvsor /*2nd test*/

  2  where b  = 1 or a = 1003 ;

1003 rows selected.

Execution Plan

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

   0      SELECT STATEMENT Optimizer=CHOOSE

   1    0   CONCATENATION

   2    1     TABLE ACCESS (BY INDEX ROWID) OF 'UNIONVSOR'

   3    2       INDEX (RANGE SCAN) OF 'UA' (NON-UNIQUE)

   4    1     TABLE ACCESS (BY INDEX ROWID) OF 'UNIONVSOR'

   5    4       INDEX (RANGE SCAN) OF 'UB' (NON-UNIQUE)

Statistics

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

          0  recursive calls

          0  db block gets

        143  consistent gets

          0  physical reads

          0  redo size

      63749  bytes sent via SQL*Net to client

       7751  bytes received via SQL*Net from client

         68  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

       1003  rows processed

 

SQL> select * from unionvsor /*3rd test*/

  2  where a = 1003

  3  union

  4   select * from unionvsor

  5   where b = 1;

1003 rows selected.

Execution Plan

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

   0      SELECT STATEMENT Optimizer=CHOOSE

   1    0   SORT (UNIQUE)

   2    1     UNION-ALL

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