Mysql
1、判断一个表是否存在
语法:
SELECT table_name FROM information_schema.TABLES WHERE table_name ='表名';
sql例子:
SELECT table_name FROM information_schema.TABLES WHERE table_name ='t_iov_vehicle_owner_info'
存在:
不存在:
备注,sql也可以这样写:
select count(*) from information_schema.tables where table_name='t_iov_vehicle_owner_info'
2、判断表中一个字段是否存在
语法:
select count(*) from information_schema.columns where table_name = '表名' and column_name = '字段名'
sql例子:
select count(*) from information_schema.columns where table_name = 't_iov_vehicle_owner_info' and column_name = 'id'
存在:
不存在:
知识点延伸:
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、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';
3、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';