Sql Interview Practice Questions
SQL Interview Practice Questions
Sql Interview Practice Questions
SQL interview practice questions are commonly used to assess a candidate's knowledge and skills in SQL (Structured Query Language) for database management. These questions typically cover topics such as data querying, data manipulation, data definition, and database normalization. By practicing SQL interview questions, candidates can improve their problem-solving abilities, SQL syntax expertise, and understanding of database concepts, which can help them succeed in SQL-related job interviews.
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1 - What is SQL? Answer: SQL (Structured Query Language) is a programming language used for managing and manipulating relational databases. It allows users to retrieve, update, insert, or delete data stored in a database.
2) Explain the difference between SQL and MySQL. Answer: SQL is a standardized language for working with databases, while MySQL is a relational database management system that uses SQL as its language to interact with databases.
3) What are CRUD operations in SQL? Answer: CRUD stands for Create, Read, Update, and Delete. These operations are used to manage data in a database. Create is for inserting new records, Read is for retrieving data, Update is for modifying existing records, and Delete is for removing records.
4) What is a primary key in SQL? Answer: A primary key is a unique identifier for each record in a table. It ensures that each record can be uniquely identified and helps maintain data integrity.
5) Explain the difference between INNER JOIN and LEFT JOIN in SQL. Answer: INNER JOIN returns rows when there is at least one match in both tables being joined, while LEFT JOIN returns all rows from the left table and the matched rows from the right table. If there are no matches in the right table, NULL values are returned.
6) What is a foreign key in SQL? Answer: A foreign key is a field in a table that is a primary key in another table. It establishes a relationship between two tables in a database.
7) Write a SQL query to find the second highest salary from an Employee table. Answer: SELECT MAX(salary) FROM Employee WHERE salary < (SELECT MAX(salary) FROM Employee);
8) What is normalization in SQL? Answer: Normalization is the process of organizing data in a database efficiently. It involves reducing data redundancy and improving data integrity by dividing tables into smaller, related tables.
9) Explain the ACID properties in SQL. Answer: ACID stands for Atomicity, Consistency, Isolation, and Durability. These properties ensure that database transactions are processed reliably and consistently.
10) What is a view in SQL? Answer: A view is a virtual table created by a query that can be used like a regular table. It provides a way to simplify complex queries and restrict access to specific data for users.
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