oracle新建空表,oracle 11g r2 新建空表不分配semgent

oracle 11g以前，建立空表也会分配段占用磁盘空间，如果查出库中所有没有记录的空表呢？呵今天无意间发现一怪语法

anbob@ANBOB> set echo off heading off feedback off lines 100 pages 0;

anbob@ANBOB> spool tmp.sql

anbob@ANBOB> select 'select ''' || table_name || ''' from ' || table_name || ' having count(*) = 0;' from user_tables;

anbob@anbob>spool off

查看一下生成的tmp.sql，

sql>@tmp.sql

select 'TESTEXPDP' from TESTEXPDP having count(*) = 0;

select 'TESTCOMP' from TESTCOMP having count(*) = 0;

select 'TESTTAB' from TESTTAB having count(*) = 0;

select 'TESTTAB_IME' from TESTTAB_IME having count(*) = 0;

select 'TESTTAB_DEF' from TESTTAB_DEF having count(*) = 0;

....

看到的是什么？呵呵，就是没有记录的表名

当然不如果不费时间也可以用统计信息数据字典

sql> exec dbms_stats.gather_schema_stats(‘anbob’);

PL/SQL procedure successfully completed.

sql> conn anbob/anbob Connected. anbob@ORCL> select table_name from user_tables where num_rows=0;