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'