查询中使用数值函数 
==============================



常用数值函数有：sum(求和)、avg(求平均)、ceil(向上取整)、floor(向下取整)、trunc(数值取整)、round(n)(四舍五入保留n位小数)。

如求历史表中每个仓库和区域的总销售额和平均每单销售额，SQL 如下： 

```javascript
SELECT  h_w_id, h_d_id, sum(h_amount) sum_h_amount , avg(h_amount) avg_h_amount 
FROM hist 
GROUP BY h_w_id, h_d_id ;
```



查询结果如下：​![](https://cdn.nlark.com/yuque/0/2020/png/177325/1600744747117-29d3b100-ef57-4f96-bc51-a8f6d026003d.png)

```unknow
​+--------+--------+--------------+--------------+
| h_w_id | h_d_id | sum_h_amount | avg_h_amount |
+--------+--------+--------------+--------------+
|      1 |      1 |       120.00 |    10.000000 |
|      1 |      2 |       120.00 |    10.000000 |
|      1 |      3 |       120.00 |    10.000000 |
|      1 |      4 |       120.00 |    10.000000 |
|      1 |      5 |       120.00 |    10.000000 |
|      1 |      6 |       120.00 |    10.000000 |
|      1 |      7 |       120.00 |    10.000000 |
|      1 |      8 |       120.00 |    10.000000 |
|      1 |      9 |       120.00 |    10.000000 |
|      1 |     10 |       120.00 |    10.000000 |
|      2 |      1 |       120.00 |    10.000000 |
|      2 |      2 |       120.00 |    10.000000 |
|      2 |      3 |       120.00 |    10.000000 |
|      2 |      4 |       120.00 |    10.000000 |
|      2 |      5 |       120.00 |    10.000000 |
|      2 |      6 |       120.00 |    10.000000 |
|      2 |      7 |       120.00 |    10.000000 |
|      2 |      8 |       120.00 |    10.000000 |
|      2 |      9 |       120.00 |    10.000000 |
|      2 |     10 |       120.00 |    10.000000 |
+--------+--------+--------------+--------------+
20 rows in set (0.01 sec)
```