一道群友分享的MySQL面试真题，你会吗？
其实常见的MySQL面试题，并不会太难，比如说下面这道行转列的题目，就是之前在去群里面看到一位群友发布的面试题目，这道题目也是数据库面试中，经常会碰到的题型，但是你是否能够很快写出这个答案来呢？
建表语句
create table student (
id varchar(20),
name varchar(20),
gender char(1),
birth varchar(20),
department varchar(20),
address varchar(20)
) charset = utf8;插入数据
insert into student values
("201901","张大佬","男","1985","计算机系","北京市海淀区"),
("201902","郭大侠","男","1986","中文系","北京市昌平区"),
("201903","张三","女","1990","中文系","湖南省永州市"),
("201904","李四","男","1990","英语系","辽宁市阜新市"),
("201905","王五","女","1991","英语系","福建省厦门市"),
("201906","王六","男","1988","计算机系","湖南省衡阳市");结果如下
第一步
select
department 院系,
case gender when "男" then 1 else 0 end 男,
case gender when "女" then 1 else 0 end 女
from student;结果如下
第二步
select
院系,
sum(男) 男,
sum(女) 女,
sum(男) + sum(女) as 总计
from
(
select department 院系,
case gender when "男" then 1 else 0 end 男,
case gender when "女" then 1 else 0 end 女
from student
) a
group by 院系;结果如下
END
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