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集合函数一共有五个
首先创建一个表
http://www.ipbbs.net/viewtopic.php?id=165
avg(), count(), max(), min(), sum();
产看商品的评价价格
mysql> select avg(g_price) from goods; +--------------+ | avg(g_price) | +--------------+ | 5.100000 | +--------------+ 1 row in set (0.00 sec)
所有厂家提供的 aaa 产品的平均价格
mysql> select avg(g_price) from goods group by g_name having g_name = 'aaa'; +--------------+ | avg(g_price) | +--------------+ | 2.100000 | +--------------+ 1 row in set (0.02 sec)
所有厂家,提供aaa 产品的最高价格
mysql> select max(g_price) from goods group by g_name having g_name = 'aaa'; +--------------+ | max(g_price) | +--------------+ | 3.10 | +--------------+ 1 row in set (0.00 sec)
获得价格最高的一行数据
mysql> select * from goods where g_price = (select max(g_price) from goods); +------+--------+------+---------+ | g_id | g_name | v_id | g_price | +------+--------+------+---------+ | 9 | ccc | 3 | 9.10 | +------+--------+------+---------+ 1 row in set (0.00 sec)
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