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

SELECT * FROM table1 JOIN table2 ON table1.id = table2.id
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：

SELECT customer, SUM(price) FROM orderGROUP BY customer HAVING SUM(price)<2000
SELECT customer,SUM(price) FROM orderWHERE customer=’…’ OR customer = ‘…’ GROUP BY customer HAVING SUM(price) > 1500