MySQL 查询获取每列的值总数，其中每列的值数量相同?
mysqlmysqli database
您可以使用聚合函数 SUM() 来实现此目的。让我们首先创建一个表 −
mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstValue int, SecondValue int, ThirdValue int ); Query OK, 0 rows affected (0.57 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable(FirstValue,SecondValue,ThirdValue) values(10,20,30); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable(FirstValue,SecondValue,ThirdValue) values(60,50,40); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable(FirstValue,SecondValue,ThirdValue) values(80,90,100); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable(FirstValue,SecondValue,ThirdValue) values(20,10,0); Query OK, 1 row affected (0.23 sec)
以下是使用 select 语句显示表中的所有记录的查询 −
mysql> select *from DemoTable;
这将产生以下输出 −
+----+------------+-------------+------------+ | Id | FirstValue | SecondValue | ThirdValue | +----+------------+-------------+------------+ | 1 | 10 | 20 | 30 | | 2 | 60 | 50 | 40 | | 3 | 80 | 90 | 100 | | 4 | 20 | 10 | 0 | +----+------------+-------------+------------+ 4 rows in set (0.00 sec)
以下查询用于获取每列的总和，其中每列具有相同数量的值 −
mysql> select sum(FirstValue),sum(SecondValue),sum(ThirdValue) from DemoTable;
这将产生以下输出 −
+-----------------+------------------+-----------------+ | sum(FirstValue) | sum(SecondValue) | sum(ThirdValue) | +-----------------+------------------+-----------------+ | 170 | 170 | 170 | +-----------------+------------------+-----------------+ 1 row in set (0.00 sec)
