Welcome to Subscribe On Youtube
Formatted question description: https://leetcode.ca/all/618.html
618. Students Report By Geography
A U.S graduate school has students from Asia, Europe and America. The students’ location information are stored in table
student as below.
| name | continent | |--------|-----------| | Jack | America | | Pascal | Europe | | Xi | Asia | | Jane | America |
Pivot the continent column in this table so that each name is sorted alphabetically and displayed underneath its corresponding continent. The output headers should be America, Asia and Europe respectively. It is guaranteed that the student number from America is no less than either Asia or Europe.
For the sample input, the output is:
| America | Asia | Europe | |---------|------|--------| | Jack | Xi | Pascal | | Jane | | |
Follow-up: If it is unknown which continent has the most students, can you write a query to generate the student report?
For each continent, assign a line id that is automatically increment. Then use outer join to join the continents.
# Write your MySQL query statement below select America, Asia, Europe from ( select @asia := 0, @america := 0, @europe := 0 ) t, ( select @asia := @asia + 1 as Asia_Id, name as Asia from student where continent = 'Asia' order by Asia ) t1 right join ( select @america := @america + 1 as America_Id, name as America from student where continent = 'America' order by America ) t2 on Asia_Id = America_Id left join ( select @europe := @europe + 1 as Europe_Id, name as Europe from student where continent = 'Europe' order by Europe ) t3 on America_Id = Europe_Id ;