常用数据库查询判断表和字段是否存在

数据库postgresql表是否存在字段是否存在oracle

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'；

总结：以上结果为1表示存在，为0表示不存在。