MySQL 如何对列元素求和

在MySQL中使用聚合函数 sum() 对列元素求和。语法如下：

select sum(yourColumnName1) as anyVariableName1,sum(yourColumnName2) as anyVariableName2,sum(yourColumnName3) as anyVariableName3,............N from yourTableName;

为了理解上述语法，我们创建一个表。以下是创建表的查询语句：

mysql> create table SumDemoOnColumns
   > (
   > First int,  
   > Second int,
   > Third int
   > );
Query OK, 0 rows affected (0.56 sec)

使用 insert 命令在此表中插入一些数据。查询语句如下所示：

mysql> insert into SumDemoOnColumns values(10,20,30);
Query OK, 1 row affected (0.18 sec)

mysql> insert into SumDemoOnColumns values(40,50,60);
Query OK, 1 row affected (0.32 sec)

mysql> insert into SumDemoOnColumns values(70,80,90);
Query OK, 1 row affected (0.10 sec)

mysql> insert into SumDemoOnColumns values(100,110,120);
Query OK, 1 row affected (0.16 sec)

使用 select 语句显示表中的所有记录。查询语句如下所示：

mysql> select *from SumDemoOnColumns;

以下是输出结果：

+-------+--------+-------+
| First | Second | Third |
+-------+--------+-------+
|    10 |     20 |    30 |
|    40 |     50 |    60 |
|    70 |     80 |    90 |
|   100 |    110 |   120 |
+-------+--------+-------+
4 rows in set (0.00 sec)

以下是求列和的查询语句：

mysql> select sum(First) as First,sum(Second) as Second,sum(Third) as Third from SumDemoOnColumns;

以下是输出结果：

+-------+--------+-------+
| First | Second | Third |
+-------+--------+-------+
|   220 |    260 |   300 |
+-------+--------+-------+
1 row in set (0.00 sec)

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