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## 25.6. 数值函数

### 25.6.1. cast 类型转换

```
mysql> SELECT cast(SUBSTRING('123456789',1,4) as UNSIGNED) * 100;
+----------------------------------------------------+
| cast(SUBSTRING('123456789',1,4) as UNSIGNED) * 100 |
+----------------------------------------------------+
|                                             123400 |
+----------------------------------------------------+
1 row in set (0.00 sec)

```

### 25.6.2. truncate 保留小数位数

```
select profit, deficit, concat(truncate((profit / deficit)*100,2),'%') as percentage from ((select count(*) as profit from angelfund where profit > 0) as profit, (select count(*) as deficit from angelfund where profit < 0) as deficit);

```

### 25.6.3. MOD 求余

```
mysql> select 9 mod 5;
+---------+
| 9 mod 5 |
+---------+
|       4 |
+---------+
1 row in set (0.00 sec)

mysql> select mod(5,2);
+----------+
| mod(5,2) |
+----------+
|        1 |
+----------+
1 row in set (0.00 sec)

mysql> select mod(5,2);

```