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# 数学运算符符号
<a name="OPERATOR_SYMBOLS"></a>

 下表列出了支持的数学运算符。

## 支持的运算符
<a name="OPERATOR_SYMBOLS-supported-operators"></a>


| 操作符  | 描述  | 示例  | 结果  | 
| --- | --- | --- | --- | 
| \+  | 加  | 2 \+ 3  | 5  | 
| -  | 减  | 2 - 3  | –1  | 
| \*  | 乘  | 2 \* 3  | 6  | 
| /  | 除  | 4 / 2  | 2  | 
| %  | 取模  | 5 % 4  | 1  | 
| ^  | 幂  | 2.0 ^ 3.0  | 8  | 

## 示例
<a name="OPERATOR_SYMBOLS-examples"></a>

为给定交易计算支付的佣金加 2.00 美元手续费：

```
select commission, (commission + 2.00) as comm
from sales where salesid=10000;

commission | comm
-----------+-------
28.05      | 30.05
(1 row)
```

为给定交易计算销售价格的 20%：

```
select pricepaid, (pricepaid * .20) as twentypct
from sales where salesid=10000;

pricepaid | twentypct
----------+-----------
187.00    |    37.400
(1 row)
```

根据持续增长模式预测票的销售量。在此示例中，子查询将返回 2008 年销售的票数。在此后 10 年，该结果将以 5% 的连续增长率呈指数增长。

```
select (select sum(qtysold) from sales, date
where sales.dateid=date.dateid and year=2008)
^ ((5::float/100)*10) as qty10years;

qty10years
------------------
587.664019657491
(1 row)
```

查找带有大于或等于 2000 的日期 ID 的销售的总支付价格和总佣金。然后将总支付价格减去总佣金。

```
select sum (pricepaid) as sum_price, dateid,
sum (commission) as sum_comm, (sum (pricepaid) - sum (commission)) as value
from sales where dateid >= 2000
group by dateid order by dateid limit 10;

 sum_price | dateid | sum_comm |   value
-----------+--------+----------+-----------
 364445.00 |   2044 | 54666.75 | 309778.25
 349344.00 |   2112 | 52401.60 | 296942.40
 343756.00 |   2124 | 51563.40 | 292192.60
 378595.00 |   2116 | 56789.25 | 321805.75
 328725.00 |   2080 | 49308.75 | 279416.25
 349554.00 |   2028 | 52433.10 | 297120.90
 249207.00 |   2164 | 37381.05 | 211825.95
 285202.00 |   2064 | 42780.30 | 242421.70
 320945.00 |   2012 | 48141.75 | 272803.25
 321096.00 |   2016 | 48164.40 | 272931.60
(10 rows)
```