在单个MySQL查询中获得多个计数以获取特定的列值
为此，您可以将聚合函数sum()与特定列的参数值一起使用。让我们首先创建一个表-
mysql> create table DemoTable1790
(
Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
Name varchar(20),
Score int
);使用插入命令在表中插入一些记录-
mysql> insert into DemoTable1790(Name,Score) values('Chris',45);
mysql> insert into DemoTable1790(Name,Score) values('David',55);
mysql> insert into DemoTable1790(Name,Score) values('David',98);
mysql> insert into DemoTable1790(Name,Score) values('Chris',91);
mysql> insert into DemoTable1790(Name,Score) values('Mike',99);
mysql> insert into DemoTable1790(Name,Score) values('Carol',55);使用select语句显示表中的所有记录-
mysql> select * from DemoTable1790;
这将产生以下输出-
+----+-------+-------+ | Id | Name | Score | +----+-------+-------+ | 1 | Chris | 45 | | 2 | David | 55 | | 3 | David | 98 | | 4 | Chris | 91 | | 5 | Mike | 99 | | 6 | Carol | 55 | +----+-------+-------+ 6 rows in set (0.00 sec)
这是在单个MySQL查询中获取多个计数的查询-
mysql> select sum(Name='Chris'),sum(Score=55) from DemoTable1790;
这将产生以下输出-
+-------------------+---------------+ | sum(Name='Chris') | sum(Score=55) | +-------------------+---------------+ | 2 | 2 | +-------------------+---------------+ 1 row in set (0.00 sec)