USING & HAVING

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

使用 USING 可以写为

SELECT * FROM table1
JOIN table2 USING(id)

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 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：

SELECT  customer,SUM(price) FROM order
WHERE customer=’…’ OR customer = ‘…’
GROUP BY customer
HAVING SUM(price) > 1500