[面试题]关于数据库查询 mysql

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怎么把这样一个表
year  month amount
1991 1    1.1
1991 2     1.2
1991 3    1.3
1991 4     1.4
1992 1     2.1
1992 2    2.2
1992 3    2.3
1992 4    2.4
查成这样一个结果
year m1   m2   m3 m4
1991 1.1 1.2 1.3 1.4
1992 2.1 2.2 2.3 2.4

Year

MySQL

amount

month

2 replies

Efraim

Apr 26, 2018

select year ,sum(if(month=1,amount,0)) as m1,sum(if(month=2,amount,0)) as m2,sum(if(month=3,amount,0)) as m3,sum(if(month=4,amount,0)) as m4 from test group by year;

adli007

Apr 27, 2018

@Efraim 多谢了又学到了 if()函数