MySQL 如何将Count(*)实现为变量以显示表中记录数

可以在MySQL中使用别名作为变量名，如下所示的语法-

select count(*) AS anyAliasName from yourTableName;

首先让我们创建一个表 –

mysql> create table DemoTable695 (
   FirstName varchar(100)
);
Query OK, 0 rows affected (0.72 sec)

使用insert命令向表中插入一些记录 –

mysql> insert into DemoTable695 values('Chris');
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable695 values('Robert');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable695 values('David');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable695 values('Mike');
Query OK, 1 row affected (0.16 sec)

使用select语句显示表中所有记录 –

mysql> select *from DemoTable695;

这将产生以下输出 –

+-----------+
| FirstName |
+-----------+
| Chris     |
| Robert    |
| David     |
| Mike      |
+-----------+
4 rows in set (0.00 sec)

以下是在MySQL中将Count(*)视为变量的查询 –

mysql> select count(*) AS TOTAL_NO_OF_RECORDS from DemoTable695 ;

这将产生以下输出 –

+---------------------+
| TOTAL_NO_OF_RECORDS |
+---------------------+
| 4                   |
+---------------------+
1 row in set (0.02 sec)

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