常用数据库查询之一（判断表和字段是否存在）

 

参数table_name和column_name的值均为大写：

 

1、MSSQL Server
 
  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'；

2、My SQL
 
  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'；

3、Oracle
 
  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'；

4、PostgreSql
 
  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' and table_name ='table_name' and  column_name='column_name'；