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法律研究如何使用 MySQL GROUP BY 从特定公司中获取员工姓名？
我们先创建一个表 -
mysql> create table DemoTable642( EmployeeId int NOT NULL AUTO_INCREMENT PRIMARY KEY,EmployeeName archar(100), EmployeeCompanyNamevarchar(100) ); Query OK, 0 rows affected (0.81 sec)
使用插入命令向表中插入一些记录 -
mysql> insert into DemoTable642(EmployeeName,EmployeeCompanyName) values('John','Google');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable642(EmployeeName,EmployeeCompanyName) values('Carol','Microsoft');
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable642(EmployeeName,EmployeeCompanyName) values('John','Amazon');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable642(EmployeeName,EmployeeCompanyName) values('Carol','Google');
Query OK, 1 row affected (0.37 sec)
mysql> insert into DemoTable642(EmployeeName,EmployeeCompanyName) values('John','Flipkart');
Query OK, 1 row affected (0.14 sec)使用 select 语句显示表中的所有记录 -
mysql> select *from DemoTable642;
这将产生以下输出 -
+------------+--------------+---------------------+ | EmployeeId | EmployeeName | EmployeeCompanyName | +------------+--------------+---------------------+ | 1 | John | Google | | 2 | Carol | Microsoft | | 3 | John | Amazon | | 4 | Carol | Google | | 5 | John | Flipkart | +------------+--------------+---------------------+ 5 rows in set (0.00 sec)
以下是从特定公司获取员工姓名的查询 -
mysql> select EmployeeName from DemoTable642 where EmployeeCompanyName="Google" group by EmployeeName;
这将产生以下输出 -
+--------------+ | EmployeeName | +--------------+ | John | | Carol | +--------------+ 2 rows in set (0.00 sec)
更新时间： 2019 年 8 月 23 日
128 次浏览
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