MySQL USING 和 HAVING 用法

USING

用于表连接时给定连接条件(可以理解为简写形式),如

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SELECT * FROM table1  

JOIN table2 ON table1.id = table2.id  

使用 USING 可以写为

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SELECT * FROM table1  

JOIN table2 USING(id)  

就这么简单

HAVING

引入 HAVING 是因为 WHERE 无法和统计函数一起使用

如表 order (定单)有如下字段:

id, date, price, customer

查找订单总额少于2000的客户可以这样写:

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SELECT customer, SUM(price) FROM order  

GROUP BY customer  

HAVING SUM(price)<2000  

查找指定客户中订单超过1500的订单总额:

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SELECT  customer,SUM(price) FROM order  

WHERE customer=’…’ OR customer = ‘…’  

GROUP BY customer  

HAVING SUM(price) > 1500  

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