Q101. What does ROLLBACK do after COMMIT?
**`ROLLBACK` does nothing after a `COMMIT` has executed**. ### Why? Once a transaction issues `COMMIT`, the changes are permanently written to the database transaction lo...
Technical Question Bank · Peer-Reviewed
Job Interview Questions and Answers Directory
Search and filter frequently asked interview questions across technical, programming, and behavioral domains. Tailor your interview preparation by difficulty for freshers or experienced developers (115 available).
Active:
Tag: rdbms ×
Q102. Valid properties of a transaction?
The four foundational properties that guarantee database transactions are processed reliably are known as **ACID**: 1. **Atomicity**: "All or nothing." If any statement w...
Q103. What if autocommit is enabled?
Every individual statement is automatically committed. In MySQL, autocommit is ON by default. Turn it off for multi-statement transactions: ```sql SET autocommit = 0; -- ...
Q104. Default isolation level in MySQL?
**REPEATABLE READ** (InnoDB engine). Prevents dirty reads and non-repeatable reads, but phantom reads are possible (though InnoDB uses MVCC + gap locking to mostly preven...
Q105. Is autocommit enabled by default in MySQL?
**Yes**, in MySQL (using the standard InnoDB storage engine), **autocommit is enabled by default** (`autocommit = 1`): ### What Autocommit Means: - Every individual SQL s...
Q106. What is a virtual table in MySQL?
In MySQL and relational databases, a **virtual table** is called a **View**: ```sql CREATE VIEW active_customer_summary AS SELECT id, first_name, last_name, email FROM Cu...
Q107. Are views updatable?
**Some views are updatable, but under strict structural criteria**: ### Conditions for a View to Be Updatable: 1. Must reference **only one base table** in the `FROM` cla...
Q108. Advantages of views?
1. **Simplify complex queries** — hide JOINs and aggregations 2. **Security** — expose only specific columns/rows 3. **Logical independence** — shield apps from schema ch...
Q109. Does a view contain data?
**Standard SQL views do NOT contain data**. - **Standard Views (Virtual)**: Contain only a stored SQL query definition in the data dictionary. Every query against the vie...
Q110. How to remove a view?
To delete a view from the database, use the **`DROP VIEW`** command: ```sql DROP VIEW IF EXISTS active_customer_summary; ``` Dropping a view removes only the stored query...