[Solved] Consider the table attendance with columns class, student, and date. What does this query return?SELECT class, date, COUNT(student) FROM attendance GROUP BY class, date; | SQL

SQL - GROUP BY and HAVING

Consider the table attendance with columns class, student, and date. What does this query return?

SELECT class, date, COUNT(student) FROM attendance GROUP BY class, date;

ANumber of students per class per date

BNumber of classes per student per date

CNumber of dates per class per student

DTotal students in the attendance table

Step-by-Step Solution

Solution:

Step 1: Identify grouping columns
The query groups rows by class and date, so each group is a unique class-date pair.
Step 2: Understand COUNT(student)
COUNT(student) counts how many students attended each class on each date.
Final Answer:
Number of students per class per date -> Option A
Quick Check:
COUNT with GROUP BY multiple columns counts per unique pairs [OK]

Quick Trick: COUNT with GROUP BY multiple columns counts per group [OK]

Common Mistakes:

MISTAKES

Mixing grouping columns order
Misinterpreting COUNT as total table count
Confusing columns in SELECT and GROUP BY

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More SQL Quizzes

Consider the table attendance with columns class, student, and date. What does this query return?

Step 1: Identify grouping columns

Step 2: Understand COUNT(student)

Final Answer:

Quick Check:

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