mysql如何转置

Mysql 行列转置可以

select name,

sum(if(subject='语文',grade,0) as 语文, sum(if(subject='数学',grade,0) as 数学,

sum(if(subject='英语',grade,0) as 英语

from scores

1、创建三张测试表，

create table pw_memberinfo(uid int, name varchar(20))

create table pw_members(companyid int, uid int)

create table pw_memberdata(uid int, deposit int, ddeposit int, money int)

2、三张表，分别插入测试数据，

insert into pw_members values(1, 1)

insert into pw_members values(1, 2)

insert into pw_members values(1, 3)

insert into pw_memberinfo values(1, 'name_1')

insert into pw_memberinfo values(2, 'name_2')

insert into pw_memberinfo values(3, 'name_3')

insert into pw_memberdata values(1,30,50,150)

insert into pw_memberdata values(2,77,50,12)

insert into pw_memberdata values(3,44,50,82)

3、查看pw_memberdata表中的记录，select * from pw_memberdata t，

4、编写sql语句，

select * from (SELECT i.uid, sum(deposit+ddeposit+money) as allmoney

FROM pw_memberinfo i

LEFT JOIN pw_members m ON m.uid=i.uid

LEFT JOIN pw_memberdata d ON i.uid=d.uid

group by i.uid

) t where allmoney>200

您好，单个select语句实现MySQL查询统计次数的方法用处在哪里呢？用处太多了，比如一个成绩单，你要查询及格得人数与不及格的人数，怎么一次查询出来？

MySQL查询统计次数简单的语句肯定是这样了：

select a.name,count_neg,count_plus from

(select count(id) as count_plus,name from score2 where score >=60 group by name) a,

(select count(id) as count_neg,name from score2 where score <=60 group by name) b

where a.name=b.name

即必须至少用2个语句。

今天刚好碰到发现mysql支持if，那就创造性的用if来实现吧：

select name, sum(if(score>=60,1,0)),sum(if(score<60,1,0)) from score2 group by name

单个select语句实现MySQL查询统计次数的方法简单吧。

原理就是大于60，就赋值为1，那么sum就是计数了。

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