mysql插入前判断数据是否存在

 

转：https://blog.csdn.net/lai0yuan/article/details/78234102

可以插入前进行判断要插入的数据是否存在业务代码如下 ：

INSERT INTO t_topic_vistor(user_id,topic_code) SELECT '218', 
'XQ33019920170811142528217' FROM DUAL WHERE NOT EXISTS(SELECT * 
FROM t_topic_vistor WHERE user_id = 218 and 
topic_code='XQ33019920170811142528217')

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语法如下：

INSERT INTO table(field1, field2, fieldn) SELECT 'field1', 
'field2', 'fieldn' FROM DUAL WHERE NOT EXISTS(SELECT field FROM 
table WHERE field = ?)