01
What is the difference between COUNT(*) and COUNT(column)?
Show answer
COUNT(*) counts all rows; COUNT(column) counts only rows where that column is not NULL.
216 medium questions with answers. Applied questions that check whether you can use the concepts on real work.
Anyone with some hands-on practice: most real interview time is spent on medium questions like these.
Answer each question aloud before opening the answer, mark it as solved only when your answer matches the key idea, and save misses to Last-Minute Revision.