47 lines
2.5 KiB
Markdown
47 lines
2.5 KiB
Markdown
|
---
|
|||
|
|
title: SQL Sum Function
|
|||
|
|
localeTitle: SQL求和函数
|
|||
|
|
---
|
|||
|
|
## SQL求和函数
|
|||
|
|
|
|||
|
|
这是聚合函数之一（如计数，平均值，最大值，最小值等）。它们在GROUP BY子句中使用，因为它聚合语句的SELECT FROM WHERE部分所呈现的数据。
|
|||
|
|
|
|||
|
|
### 使用示例
|
|||
|
|
|
|||
|
|
SELECT语句中的“sum（Total\_ $）”聚合在GROUP BY子句中。 “Count（\*）”提供了贡献的数量。
|
|||
|
|
|
|||
|
|
这些数据来自我们在其中一些指南中使用的广告系列贡献数据。
|
|||
|
|
|
|||
|
|
这个SQL语句正在回答这个问题：“哪些候选人在2016年获得了最大的总捐款额，但只有那些超过2000万美元的所有捐款合计？”
|
|||
|
|
|
|||
|
|
以降序（DESC）顺序对此数据集进行排序会将总贡献最大的候选项放在列表顶部。
|
|||
|
|
|
|||
|
|
```sql
|
|||
|
|
SELECT Candidate, Election_year, sum(Total_$), count(*)
|
|||
|
|
FROM combined_party_data
|
|||
|
|
WHERE Election_year = 2016
|
|||
|
|
GROUP BY Candidate, Election_year -- this tells the DBMS to summarize by these two columns
|
|||
|
|
HAVING sum(Total_$) > 20000000 -- limits the rows presented from the summary of money ($20 Million USD)
|
|||
|
|
ORDER BY sum(Total_$) DESC; -- orders the presented rows with the largest ones first.
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
```text
|
|||
|
|
+--------------------------------------------------+---------------+-------------------+----------+
|
|||
|
|
| Candidate | Election_year | sum(Total_$) | count(*) |
|
|||
|
|
+--------------------------------------------------+---------------+-------------------+----------+
|
|||
|
|
| CLINTON, HILLARY RODHAM & KAINE, TIMOTHY M (TIM) | 2016 | 568135094.4400003 | 126 |
|
|||
|
|
| TRUMP, DONALD J & PENCE, MICHAEL R (MIKE) | 2016 | 366853142.7899999 | 114 |
|
|||
|
|
| SANDERS, BERNARD (BERNIE) | 2016 | 258562022.17 | 122 |
|
|||
|
|
| CRUZ, RAFAEL EDWARD (TED) | 2016 | 93430700.29000005 | 104 |
|
|||
|
|
| CARSON, BENJAMIN S (BEN) | 2016 | 62202411.12999996 | 93 |
|
|||
|
|
| RUBIO, MARCO ANTONIO | 2016 | 44384313.9 | 106 |
|
|||
|
|
| BUSH, JOHN ELLIS (JEB) | 2016 | 34606731.78 | 97 |
|
|||
|
|
+--------------------------------------------------+---------------+-------------------+----------+
|
|||
|
|
7 rows in set (0.01 sec)
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
与所有这些SQL事物一样，它们比本入门指南中的内容更多。
|
|||
|
|
|
|||
|
|
我希望这至少足以让你开始。
|
|||
|
|
|
|||
|
|
请参阅您的数据库管理员手册，并自己尝试不同的选项。
|