SQL group by case example 2020-12-23 02:50
Here's an interview question about SQL. To solve this problem, we need to use group by and the case function. The table structure is as follows.
id name grade sex 1 henry 1 1 2 justin 2 1 3 Tao 1 1 4 Xia 1 0
You need to use SQL to find the total number of boys and girls in each grade.
The correct SQL looks like this
select grade,sum(case sex when 1 then 1 end) as boy,sum(case sex when 0 then 1 end) as girl from student group by grade
grade boy girl 1 2 null 2 1 1