四舍五入函数ROUND(x,y)

四舍五入函数ROUND(x,y)
参数：
x：数据
y：需要保留的小数点位数
ROUND(x,y)函数返回最接近于参数x的数，其值保留到小数点后面y位，若y为负值，则将保留x值到小数点左边y位。
mysql> select round(32.154,2);
+-----------------+
| round(32.154,2) |
+-----------------+
|           32.15 |
+-----------------+
1 row in set (0.41 sec)

mysql> select round(32.154,1);
+-----------------+
| round(32.154,1) |
+-----------------+
|            32.2 |
+-----------------+
1 row in set (0.02 sec)

mysql> select round(32.154,0);
+-----------------+
| round(32.154,0) |
+-----------------+
|              32 |
+-----------------+
1 row in set (0.00 sec)

mysql> select round(32.154,3);
+-----------------+
| round(32.154,3) |
+-----------------+
|          32.154 |
+-----------------+
1 row in set (0.00 sec)

mysql>

求所有电脑产品的平均价格,并且保留两位小数，AVG,MAX,MIN、COUNT、SUM为聚合函数
SELECT AVG(goods_price) AS avg_price FROM tdb_goods;
SELECT ROUND(avg_price,2) AS avg_price FROM tdb_goods;