如何在 MySQL 中合并几行记录?
mysqlmysqli database
为此，使用 CASE WHEN 概念。让我们首先创建一个表 −
mysql> create table demo68 −> ( −> id int not null auto_increment primary key, −> company_name varchar(50), −> employee_name varchar(50), −> country_name varchar(50) −> ); Query OK, 0 rows affected (1.86 sec)
使用 insert 命令向表中插入一些记录 −
mysql> insert into demo68(company_name,employee_name,country_name)
values('Google','John','US');
Query OK, 1 row affected (0.29 sec)
mysql> insert into demo68(company_name,employee_name,country_name)
values('Google','Bob','UK');
Query OK, 1 row affected (0.10 sec)
mysql> insert into demo68(company_name,employee_name,country_name)
values('Google','David','AUS');
Query OK, 1 row affected (0.08 sec)
使用 select 语句显示表中的记录 −
mysql> select *from demo68;
这将产生以下输出 −
+----+--------------+---------------+--------------+ | id | company_name | employee_name | country_name | +----+--------------+---------------+--------------+ | 1 | Google | John | US | | 2 | Google | Bob | UK | | 3 | Google | David | AUS | +----+--------------+---------------+--------------+ 3 rows in set (0.00 sec)
以下是在 MySQL 中合并几行记录的查询−
mysql> select −> company_name, −> max(case when country_name= 'US' then employee_name end) as US_Employee_Name, −> max(case when country_name= 'UK' then employee_name end) as UK_Employee_Name, −> max(case when country_name= 'AUS' then employee_name end) as AUS_Employee_Name −> from demo68 −> group by company_name;
这将产生以下输出 −
+--------------+------------------+------------------+-------------------+ | company_name | US_Employee_Name | UK_Employee_Name | AUS_Employee_Name | +--------------+------------------+------------------+-------------------+ | Google | John | Bob | David | +--------------+------------------+------------------+-------------------+ 1 row in set (0.05 sec)
