Q1. How does MongoDB differ from a relational database?
MongoDB is a document database. Data is stored as flexible BSON documents inside collections instead of rows in tables with a fixed schema. Each document can have its own...
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Q2. 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...
Q3. How do window functions work and when do you use them?
Window functions compute a value across a set of rows related to the current row without collapsing them, unlike GROUP BY. They preserve row granularity. ```sql SELECT us...
Q4. What does SQL stand for?
**SQL** stands for **Structured Query Language**. Originally developed at IBM by Donald D. Chamberlin and Raymond F. Boyce in the early 1970s, it was initially named **SE...
Q5. How do you prevent SQL injection in PHP?
Never concatenate user input into SQL. Use prepared statements with bound parameters, which separate code from data. ```php $stmt = $pdo->prepare('SELECT * FROM users WHE...
Q6. What type of language is SQL?
**Declarative (non-procedural)**. You state *what* result you want, not *how* to compute it. The database's **query optimizer** decides the "how" — which indexes to use, ...
Q7. Which is NOT a valid SQL command: SELECT, REMOVE, UPDATE, INSERT?
**REMOVE** is not valid. To delete rows, use `DELETE`. `DROP` removes objects (tables, databases). | Command | Purpose | |---------|---------| | SELECT | Read data | | IN...
Q8. What is the difference between SQL and NoSQL and when do you choose each?
SQL (relational): rigid schema, ACID transactions, powerful joins and ad-hoc queries, mature tooling. Excel at structured, relational data with integrity requirements suc...
Q9. What is MySQL, and how does it differ from SQL?
**SQL** is the *language* (like English). **MySQL** is a *database system* that *speaks* SQL (like a person who speaks English). Analogy: SQL is the recipe; MySQL is the ...
Q10. What is PL/SQL, and how is it different from SQL?
**PL/SQL** = Procedural Language extensions to SQL (Oracle-specific). It adds variables, loops, IF-ELSE, and exception handling. | SQL | PL/SQL | |-----|--------| | Singl...