常用数据库查询判断表和字段是否存在

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。