MySQL winter vacation self-study 2022 12 (1)

function

group_concat

Data preparation

create database mydb4;
use mydb4;

create table emp
(
	emp_id int primary key auto_increment comment ' Number ',
	emp_name char(20) not null default '' comment ' full name ',
	salary decimal(10,2) not null default 0 comment ' Wages ',
	department char(20) not null default '' comment ' department '
);
insert into emp(emp_name,salary,department) 
values(' Zhang Jingjing ',5000,' Finance Department '),
(' Wang Feifei ',5800,' Finance Department '),
(' Zhao Gang ',6200,' Finance Department '),
(' Liu Xiaobei ',5700,' The personnel department '),
(' Wang Dapeng ',6700,' The personnel department '),
(' Zhang Xiaofei ',5200,' The personnel department '),
(' Liu yunyun ',7500,' The sales department '),
(' Liu Yunpeng ',7200,' The sales department '),
(' Liu Yunpeng ',7800,' The sales department ');

part1

--  Put the names of all employees in one line 
select group_concat(emp_name) from emp;

The operation results are as follows

part2

--  Specify the separator 
select group_concat(emp_name separator ';') from emp;

  The operation results are as follows

 part 3

--  Splicing after grouping 
select department,group_concat(emp_name separator ';') from emp group by department;

part 4 Sort by salary

--  Splicing after grouping , And sort 
select department,group_concat(emp_name order by salary desc separator ';') from emp group by department;