摘要： 第一次用MySql，写出如下语句：INSERT INTO tb (id,TName) VALUES(1, 'a new name') WHERE not exists (SELECT TName FROM tb WHERE TName='a old name');报错，百思不得其解。google之后的答案：INSERT INTO tb (id,TName) SELECT 1, 'a new name' FROM dual WHERE not exists (SELECT TName FROM tb WHERE TName='a old n 阅读全文