In this article, you will discover the most commonly encountered SQL questions during a technical interview. Preparing for an SQL interview can be challenging, particularly when your role demands proficiency in advanced SQL.
This article compiles the top 25 frequently asked advanced SQL interview questions, offering comprehensive answers and additional resources for further exploration.
1. What is a Database?
A database is a structured collection of data organized coherently and shared. It is designed to enable the efficient storage, management, searching, and manipulation of data. In other words, a database is a system for storing and organizing data that allows users to access, update, and retrieve information quickly and effectively.
2. Types of databases
a. Relational Database: A relational database is a type of database that organizes data into relational tables. Data is structured and organized in rows and columns within these tables. They use relationships between tables to connect data. The standard query language for relational databases is SQL (Structured Query Language).
b. NoSQL Database: NoSQL stands for “Not Only SQL” and represents a broad category of databases that depart from the traditional relational model. NoSQL databases are designed to handle large volumes of unstructured or semi-structured data, such as documents, graphs, or key-value data. Some common types of NoSQL databases include document databases, graph databases, column databases, and key-value databases.
c. Columnar Database: A columnar database organizes data so that it is stored by columns rather than rows. This type of database is optimized for queries that require access to a subset of columns within a table. Columnar databases are often used for analytical applications where retrieving large amounts of data quickly is necessary.
d. Key-Value Database: Key-value databases are simple yet powerful. Each data item is stored as a key-value pair, where the key is a unique identifier, and the value can be any data type. These databases are optimal for applications that require fast access to information via a key. They are often used for caching, user sessions, and counting systems.
e. Graph Database: Graph databases are designed to handle highly interconnected data…