Content ITV PRO
This is Itvedant Content department
Interview Questions
Top 5 SQL Interview Questions
Learning Outcome
5
Aggregating and summarizing your data.
4
Filtering rows at different stages in SQL
3
Three ways to remove data — with key differences.
2
Combining data from multiple tables with types.
1
Understanding Constraints that enforce data integrity.
Question 1
Primary Key vs Unique Key
🔑 Primary Key :-
• ❌ NULL values are not allowed
• 1️⃣ Only one PRIMARY KEY per table
• 🆔 Uniquely identifies every row
🔑 Unique Key :-
• ⚠️ Allows one NULL value
• 🔢 Multiple UNIQUE keys per table
• ✔️ Ensures uniqueness with flexibility
Question 2
Types of Joins
Question 3
Delete vs Truncate vs Drop
🗑️ Delete
-
🔎 Supports WHERE clause
-
♻️ Can be rolled back
-
🎯 Deletes selected records only
⚡ Truncate
-
🚀 Faster than DELETE
-
❌ Cannot use WHERE clause
-
🧹 Removes all records quickly
💥 Drop
-
🗂️ Removes structure + data
-
⚠️ Cannot be undone easily
-
🗑️ Deletes the complete table
Question 4
Where vs Having
Filter Rows (WHERE)
Filter Groups (HAVING)
Group Rows (GROUP BY)
HAVING
Filters after GROUP BY. Designed to work with aggregate functions for grouped results.
WHERE
Filters rows before GROUP BY is applied. Cannot use aggregate functions like COUNT() or SUM().
Question 5
What is Group by?
You've Got This!
Walk into your SQL interview with confidence. Master these core SQL concepts and you'll stand out as a top candidate.
🚀 All the Best!
Copy of Interview Questions - Power BI
By Content ITV
