如何在 HiveSQL 中进行 vlookup？

Question

I'm new to Hive and still learning about it, but have a small problem here. Really need help on this thing..

So, I have a table of students' grade as below:

*exam_index shows how many exams each student have taken, 1 means first exam, 2 means second exam.

and I'd like to convert it into this expected result:

Any idea of doing this? Any input would be greatly appreciated. Thanks!

Answer 1

You can use conditional aggregation:

select student,
       max(case when exam_index = 1 then grade end) as grade_1,
       max(case when exam_index = 2 then grade end) as grade_2
from t
group by student;