常用数据库查询判断表和字段是否存在

         表：select  COUNT(*)  from  dbo.sysobjects WHERE name=  'table_name'；

     字段：select  COUNT(*)  from syscolumns WHERE id=object_id(‘table_name’)  and name=  'column_name'；

        表：select COUNT(*) from information_schema.tables WHERE table_name = 'table_name'；

    字段：select COUNT(*) from information_schema.columns WHERE table_name = 'table_name' and column_name = 'column_name'；

        表：SELECT count(*) FROM USER_OBJECTS WHERE  OBJECT_NAME =  'table_name'；

        字段：SELECT COUNT(*) FROM USER_TAB_COLUMNS WHERE TABLE_NAME = 'table_name' and column_name = 'column_name'；

           表：select count(*) from information_schema.tables WHERE table_schema='table_schema' and  table_name ='table_name'；

        字段：select count(*) from information_schema.columns WHERE table_schema='table_schema'