1. What is SQL?
SQL (Structured Query Language) is a programming language used for managing and manipulating relational databases.

2. What are the different types of SQL statements?
SQL statements can be broadly classified into three categories: Data Definition Language (DDL), Data Manipulation Language (DML), and Data Control Language (DCL).

3. What is the difference between SQL and NoSQL databases?
SQL databases are structured and use a tabular format to store data, while NoSQL databases are non-relational and use various data models such as key-value, document, columnar, or graph.

4. What is a primary key in SQL?
A primary key is a column or combination of columns that uniquely identifies each row in a table. It ensures data integrity and enables efficient data retrieval.

5. What is a foreign key?
A foreign key is a column or set of columns in a table that refers to the primary key of another table. It establishes relationships between tables and enforces referential integrity.

6. What is the difference between UNION and UNION ALL in SQL?
UNION combines the result sets of two or more SELECT statements, removing duplicates, while UNION ALL combines the result sets without removing duplicates.

7. What are SQL joins?
Joins are used to combine rows from two or more tables based on related columns. Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

8. What is the difference between WHERE and HAVING clauses?
The WHERE clause is used to filter rows before grouping in a query, while the HAVING clause is used to filter groups of rows after grouping in a query.

9. What is normalization in SQL?
Normalization is the process of organizing data in a database to eliminate redundancy and ensure data integrity. It involves dividing larger tables into smaller, more manageable tables and establishing relationships between them.

10. How can you prevent SQL injection attacks?
To prevent SQL injection attacks, it is important to use parameterized queries or prepared statements, properly validate and sanitize user input, and limit the privileges of database users.