MySQL Aliases

MySQL Tutorial

🏷️ MySQL Aliases

In MySQL, aliases are temporary names given to columns or tables to make queries shorter, clearer, and more readable.

👉 Aliases exist only during query execution.

1️⃣ What are Aliases?

  • Temporary names for columns or tables

  • Improve readability

  • Useful with joins, functions, calculations

  • Do not change database structure

2️⃣ Column Alias – Basic Syntax


📌 AS is optional in MySQL.

3️⃣ Column Alias – Simple Example ⭐


✔ Output column headers become student_name, score

4️⃣ Alias Without AS (Allowed)


📌 Works the same, but AS improves readability.

5️⃣ Alias with Expressions / Functions ⭐


✔ Very common in reports & interviews

6️⃣ Table Alias – Basic Syntax


7️⃣ Table Alias with JOIN ⭐ (Most Important)


✔ Shorter
✔ More readable
✔ Essential when multiple tables have same column names

8️⃣ Aliases with GROUP BY & HAVING


📌 MySQL allows alias in HAVING (not all DBs do).

9️⃣ Aliases with ORDER BY ⭐


✔ Alias can be used in ORDER BY

🔟 Alias with Spaces (Using Quotes)


📌 Use quotes if alias has spaces.

1️⃣1️⃣ Aliases vs Actual Names ⭐ (Interview)

Feature Alias Real Name
Temporary ✔ Yes ❌ No
Stored in DB ❌ No ✔ Yes
Used for Readability Structure

1️⃣2️⃣ Common Mistakes ❌

❌ Using alias in WHERE (not allowed)

-- ❌ Wrong


✔ Correct:


📌 Interview Questions & MCQs (Very Important)

Q1. What is an alias in MySQL?

A) Permanent column name
B) Temporary name
C) Constraint
D) Index

✅ Answer: B

Q2. Is AS mandatory in MySQL aliases?

A) Yes
B) No

✅ Answer: B

Q3. Where can alias be used?

A) SELECT
B) ORDER BY
C) HAVING
D) All of the above

✅ Answer: D

Q4. Can alias be used in WHERE clause?

A) Yes
B) No

✅ Answer: B

Q5. Which is correct?

SELECT COUNT(*) total FROM students;

A) Correct
B) Incorrect

✅ Answer: A

Q6. Why are table aliases important in JOINs?

A) Faster execution
B) Reduce storage
C) Avoid ambiguity
D) Create indexes

✅ Answer: C

🔥 Real-Life Use Cases

✔ Cleaner reports
✔ Complex JOIN queries
✔ Calculated columns
✔ Business-friendly column names

✅ Summary

  • Aliases give temporary names

  • Used for columns & tables

  • Improve readability

  • Essential in JOINs & reports

  • AS is optional

  • Cannot be used in WHERE

  • Important for SQL exams & interviews

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