SQL GROUP BY Practice Exercise: Candidate Skills [LinkedIn SQL Interview Question]

This SQL GROUP BY exercise uses real data from a LinkedIn SQL Interview question which is a bit too hard to tackle right now, so we'll solve an easier variant of the interview question.

Suppose you are given a table of candidates and their skills. How many candidates possess each of the different skills? Sort your answers based on the count of candidates, from highest to lowest.

Assumption:

• There are no duplicates in the table.

Table:

Example Input:

Example Output:

Here's the solution:

Since we have to count candidates, that's a hint to use the aggregate function!

We also want to report our count FOR EACH SKILL... which means in your head, know that we'll !

Finally, because we want to sort answers based on the count of candidates, from highest to lowest, that's a job for . We need that DESC keyword, because the default is to sort ASC (ascending), which for numerical data means lowest to highest (which is NOT what the problem wants!).