下面介绍Mysql和Sqlite和Sqlserver中，根据select的条件判断是否插入。例如：

一、Mysql中：

INSERT INTO books (name) SELECT 'msg' FROM dual WHERE NOT EXISTS (SELECT id FROM books WHERE id = 1)

 

二、Sqlite中：

由于Sqlite中没有临时表：dual

所以，需要这样写

　INSERT INTO books (name)  SELECT 'msg'  WHERE NOT EXISTS (SELECT id FROM books WHERE id = 1)

三、Sqlserver中：

SqlServer中需要另一种写法：

IF NOT EXISTS (SELECT id FROM books WHERE id = 1)  INSERT INTO books (name) SELECT 'msg'