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使用MySQL计算多行并在不同列（和一行）中显示结果

2024-04-21 15:16:03 378

让我们首先创建一个表-

mysql> create table DemoTable1452
   -> (
   -> FavouriteColor varchar(50)
   -> );

使用插入命令在表中插入一些记录-

mysql> insert into DemoTable1452 values('Red');
mysql> insert into DemoTable1452 values('Yellow');
mysql> insert into DemoTable1452 values('Yellow');
mysql> insert into DemoTable1452 values('Yellow');
mysql> insert into DemoTable1452 values('Blue');
mysql> insert into DemoTable1452 values('Blue');
mysql> insert into DemoTable1452 values('Red');

使用select语句显示表中的所有记录-

mysql> select * from DemoTable1452;

这将产生以下输出-

+----------------+
| FavouriteColor |
+----------------+
| Red            |
| Yellow         |
| Yellow         |
| Yellow         |
| Blue           |
| Blue           |
| Red            |
+----------------+
7 rows in set (0.00 sec)

以下是对多行进行计数并在不同列中显示结果的查询-

mysql> select sum(FavouriteColor='Red') as NumberOfRedColor,
   -> sum(FavouriteColor='Yellow') as NumberOfYellowColor,
   -> sum(FavouriteColor='Blue') as NumberOfBlueColor
   -> from DemoTable1452;

这将产生以下输出-

+------------------+---------------------+-------------------+
| NumberOfRedColor | NumberOfYellowColor | NumberOfBlueColor |
+------------------+---------------------+-------------------+
|                2 |                   3 |                 2 |
+------------------+---------------------+-------------------+
1 row in set (0.27 sec)

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使用MySQL计算多行并在不同列（和一行）中显示结果

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