MySQL查询对多个表中的行进行计数
让我们首先创建一个表-
mysql> create table DemoTable1 (FirstName varchar(100));
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable1 values('Bob');mysql> insert into DemoTable1 values('James');
mysql> insert into DemoTable1 values('John');
mysql> insert into DemoTable1 values('David');
使用select语句显示表中的所有记录-
mysql> select *from DemoTable1;
这将产生以下输出-
+-----------+| FirstName |
+-----------+
| Bob |
| James |
| John |
| David |
+-----------+
4 rows in set (0.00 sec)
这是创建第二个表的查询-
mysql> create table DemoTable2 (Marks int);
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable2 values(98);mysql> insert into DemoTable2 values(89);
mysql> insert into DemoTable2 values(67);
mysql> insert into DemoTable2 values(34);
mysql> insert into DemoTable2 values(32);
mysql> insert into DemoTable2 values(42);
使用select语句显示表中的所有记录-
mysql> select *from DemoTable2;
这将产生以下输出-
+-------+| Marks |
+-------+
| 98 |
| 89 |
| 67 |
| 34 |
| 32 |
| 42 |
+-------+
6 rows in set (0.00 sec)
这是对多个表中的行进行计数的查询-
mysql> select(select count(*) from DemoTable1) AS First_Table_Row,
(select count(*) from DemoTable2) AS Second_Table_Row;
这将产生以下输出-
+-----------------+------------------+| First_Table_Row | Second_Table_Row |
+-----------------+------------------+
| 4 | 6 |
+-----------------+------------------+
1 row in set (0.00 sec)
以上是 MySQL查询对多个表中的行进行计数 的全部内容, 来源链接: utcz.com/z/357767.html