SQL Interview Questions and Answers

SQL Interview Questions and Answers for ...

Basic Questions

  1. What is SQL?

    • SQL stands for Structured Query Language. It is used to communicate with databases to perform tasks such as querying, updating, and managing data.

  2. What is a database?

    • A database is an organized collection of data, generally stored and accessed electronically from a computer system.

  3. What are the different types of SQL commands?

    • SQL commands are categorized into:
      • DDL (Data Definition Language): CREATE, ALTER, DROP
      • DML (Data Manipulation Language): SELECT, INSERT, UPDATE, DELETE
      • DCL (Data Control Language): GRANT, REVOKE
      • TCL (Transaction Control Language): COMMIT, ROLLBACK, SAVEPOINT

Intermediate Questions

  1. What is the difference between CHAR and VARCHAR?

    • CHAR: Fixed-length character data type.
    • VARCHAR: Variable-length character data type.

  2. What are joins in SQL?

    • Joins are used to combine rows from two or more tables based on a related column between them. Types include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

  3. What is normalization?

    • Normalization is the process of organizing data to minimize redundancy. It involves dividing a database into two or more tables and defining relationships between them.

Advanced Questions

 

  1. What is a subquery?

    • A subquery is a query nested inside another query. It can be used in SELECT, INSERT, UPDATE, or DELETE statements.

  2. What is an index?

    • An index is a database object that improves the speed of data retrieval operations on a table at the cost of additional storage and maintenance.

  3. Explain the difference between DELETE, TRUNCATE, and DROP.?

    • DELETE: Removes rows from a table based on a condition.
    • TRUNCATE: Removes all rows from a table without logging individual row deletions.
    • DROP: Deletes the entire table structure from the database.

 

Kosmik is the best SQL training institute Hyderabad,KPHB. We are providing SQL Training in hyderabad & lab facilities with complete real-time SQL training. SQL Training in Kukatpally is based on complete advance concepts. So that you can get easily "hands-on experience". We will give 100% job assistance