SQL - Aggregate Functions
What is wrong with this SQL query if we want to find the average salary per department?
SELECT Department, AVG(Salary) FROM Employees;
What is wrong with this SQL query if we want to find the average salary per department?
medium📝 Debug Q14 of 15
Step-by-Step Solution
Solution:
Step 1: Check aggregation with multiple columns
When selecting Department and AVG(Salary), Department must be grouped.Step 2: Identify missing GROUP BY
The query lacks GROUP BY Department, causing error or wrong results.Final Answer:
Missing GROUP BY clause for Department -> Option BQuick Check:
Aggregation with columns needs GROUP BY [OK]
Quick Trick: Use GROUP BY when mixing columns with aggregation [OK]
Common Mistakes:
MISTAKES- Forgetting GROUP BY with aggregation
- Thinking AVG() can't be used on numbers
- Assuming SELECT can have unrelated columns
Master "Aggregate Functions" in SQL
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