oracle中truncate和delete命令有何区别?
解决方案 »
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DELETE可以恢复
delete要写日志
在SQLPLUS下试试下面语句就知道了
SQL> set autotrace traceonly
SQL> create table t1 as select * from dba_objects;表已创建。SQL> delete from t1;已删除30484行。
执行计划
----------------------------------------------------------
0 DELETE STATEMENT Optimizer=CHOOSE
1 0 DELETE OF 'T1'
2 1 TABLE ACCESS (FULL) OF 'T1'
统计信息
----------------------------------------------------------
50 recursive calls
33930 db block gets
444 consistent gets
394 physical reads
10604052 redo size
715 bytes sent via SQL*Net to client
541 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
2 sorts (memory)
0 sorts (disk)
30484 rows processedSQL> commit;提交完成。SQL> select * from t1;未选定行
执行计划
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE
1 0 TABLE ACCESS (FULL) OF 'T1'
统计信息
----------------------------------------------------------
0 recursive calls
0 db block gets
611 consistent gets
95 physical reads
11520 redo size
918 bytes sent via SQL*Net to client
361 bytes received via SQL*Net from client
1 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
0 rows processedSQL> truncate table t1;表被截断。SQL> select * from t1;未选定行
执行计划
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE
1 0 TABLE ACCESS (FULL) OF 'T1'
统计信息
----------------------------------------------------------
0 recursive calls
1 db block gets
5 consistent gets
0 physical reads
40 redo size
918 bytes sent via SQL*Net to client
361 bytes received via SQL*Net from client
1 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
0 rows processedSQL>