操作前判断

部分摘自：http://dingchaoqun12.blog.163.com/blog/static/116062504201112554459595/

 
MySQL:

DROP TABLE IF EXISTS [table_name]

Oracle:

BEGIN      EXECUTE IMMEDIATE 'DROP TABLE [table_name]';      

EXCEPTION WHEN OTHERS THEN NULL;  END;

SQL Server:

IF EXISTS (      SELECT  TABLE_NAME FROM INFORMATION_SCHEMA.TABLES    

  WHERE   TABLE_NAME = '[table_name]')  DROP TABLE  [table_name]

Sybase

 if exists (select 1
            from  sysobjects
            where id = object_id('[TABLENAME]')
            and   type = 'U')
   drop table TABLENAME