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：sel
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'；
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