<pre name="code" class="sql">关于group by 排序问题 10g 以前sort group by 需要排序 10g 以后 hash group by 不需要排序 SQL> set linesize 200 SQL> set pagesize 200 SQL> set autot trace SQL> select owner,count(*) from t1 group by owner; 已选择30行。 执行计划 ---------------------------------------------------------- Plan hash value: 136660032 --------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 30 | 180 | 2014 (2)| 00:00:25 | | 1 | HASH GROUP BY | | 30 | 180 | 2014 (2)| 00:00:25 | | 2 | TABLE ACCESS FULL| T1 | 580K| 3403K| 1998 (1)| 00:00:24 | --------------------------------------------------------------------------- 统计信息 ---------------------------------------------------------- 0 recursive calls 0 db block gets 8323 consistent gets 8313 physical reads 0 redo size 1059 bytes sent via SQL*Net to client 426 bytes received via SQL*Net from client 3 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 30 rows processed