Q1. SQL was developed as an integral part of...
Relational Database Management Systems (RDBMS). SQL is the ANSI-standard language for creating, querying, updating, and managing relational databases. Major implementatio...
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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 (10 available).
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Q2. What are the possible values for a BOOLEAN field in MySQL?
MySQL doesn't have a native `BOOLEAN` type. It uses `TINYINT(1)` where `0` = false, `1` = true, and any non-zero value is treated as true in conditions. ```sql CREATE TAB...
Q3. How do idempotency keys work for POST requests?
The client generates a unique key per logical operation and sends it in a header, typically `Idempotency-Key`. ```http POST /payments Idempotency-Key: 4d7c2e6a-2b1f-4f9a-...
Q4. How to select 10 random rows?
```sql -- MySQL SELECT * FROM tbl ORDER BY RAND() LIMIT 10; -- PostgreSQL SELECT * FROM tbl ORDER BY RANDOM() LIMIT 10; -- SQL Server SELECT TOP 10 * FROM tbl ORDER BY NE...
Q5. What does UPPER do?
Converts to uppercase. `LOWER` to lowercase. `INITCAP` (Oracle/PostgreSQL) capitalizes first letter of each word. ```sql SELECT UPPER('hello'); -- HELLO ```
Q6. Current date in MySQL without time?
In MySQL, you retrieve the current date (year, month, day) without the time component using **`CURDATE()`** or **`CURRENT_DATE`**: ```sql SELECT CURDATE(); -- Example: '2...
Q7. Top 3 students by mark?
```sql -- MySQL / PostgreSQL SELECT name, mark FROM Students ORDER BY mark DESC LIMIT 3; -- SQL Server SELECT TOP 3 name, mark FROM Students ORDER BY mark DESC; -- Oracle...
Q8. Which set operator for "searched but didn't buy"?
`MINUS` (Oracle) or `EXCEPT` (PostgreSQL/SQL Server): ```sql SELECT name FROM searchers WHERE product = 'X' EXCEPT SELECT name FROM buyers WHERE product = 'X'; ``` ---
Q9. What is AUTO_INCREMENT?
Automatically generates sequential unique integers for a column, typically the PRIMARY KEY. ```sql CREATE TABLE users (id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(50)...
Q10. Rename column Address to Addr in Customer?
```sql -- MySQL ALTER TABLE Customer CHANGE Address Addr VARCHAR(50); -- PostgreSQL / Standard ALTER TABLE Customer RENAME COLUMN Address TO Addr; ```