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;