Oracle
=======================
Sybase
=======================
=======================
select table_name from user_tables; //当前用户的表
select table_name from all_tables; //所有用户的表
select table_name from dba_tables; //包括系统表
select table_name from dba_tables where owner='用户名'
Sybase
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select count(1) from sysobjects where type='U'