SQL Interview Questions That Test Real Skills
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08 Jan, 2025
SQL Interview Questions Your Ultimate Guide
In SQL, NULL represents the absence of a value or an unknown value. It is different from an empty string or zero; NULL simply means that the value is missing or undefined. Handling NULL values correctly is crucial to ensure data integrity and avoid unexpected behavior in queries. Here are several ways to handle NULL values in SQL:
08 Jan, 2025
SQL Interview Questions and Answers Updated
SQL (Structured Query Language) is a standardized programming language used for managing and manipulating relational databases. It is primarily used to interact with databases by querying, updating, inserting, and deleting data. SQL is essential for tasks related to database management and is widely used in various industries for backend development, data analysis, and more.
08 Jan, 2025
SQL Interview Questions and Answers
To find the Nth highest salary from a table, you can use the following approaches, depending on the SQL dialect you're working with. Below is a common approach using a subquery and the LIMIT/OFFSET clause (for MySQL) or ROW_NUMBER() function (for SQL Server, PostgreSQL, or Oracle).
08 Jan, 2025
Top SQL Server Interview Questions and Answers (2025)
The ROW_NUMBER() function in SQL is a window function that assigns a unique sequential integer to rows within a result set. The numbering starts at 1 for the first row and increments by 1 for each subsequent row in the specified order. It is typically used to assign a rank or row number to rows in a result set based on a particular order.
08 Jan, 2025
Top SQL Interview Questions and Answers
An index in SQL is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional space and time spent on updates, inserts, and deletes. Indexes are used to quickly locate and access data without having to scan the entire table. They are particularly useful for improving query performance, especially when dealing with large datasets.
07 Jan, 2025
Commonly Asked MySQL Interview Questions (2025)
In MySQL, an index is a data structure that improves the speed of data retrieval operations on a database table. Indexes are used to quickly locate and access the rows in a table based on the values of one or more columns, without having to scan the entire table. Think of an index like a book's table of contents, where you can quickly jump to the section you're interested in without reading every page.
02 Jan, 2025
Most Frequently asked Interview Questions of sqlite
The AUTOINCREMENT keyword in SQLite is used to automatically generate a unique integer value for a column, typically for a primary key. It is used in combination with the INTEGER PRIMARY KEY column type to automatically increment the value of the column each time a new row is inserted into the table. The purpose of AUTOINCREMENT is to ensure that each row has a unique identifier, which is particularly useful for the primary key field.
02 Jan, 2025
Most Frequently asked sqlite Interview Questions (2024)
The AUTOINCREMENT keyword in SQLite is used to automatically generate a unique integer value for a column, typically for a primary key. It is used in combination with the INTEGER PRIMARY KEY column type to automatically increment the value of the column each time a new row is inserted into the table. The purpose of AUTOINCREMENT is to ensure that each row has a unique identifier, which is particularly useful for the primary key field.
02 Jan, 2025
Most Frequently asked sqlite Interview Questions
SQLite is a self-contained, serverless, and zero-configuration relational database engine. Unlike traditional relational databases like MySQL and PostgreSQL, SQLite is designed to be embedded into applications. It stores all its data in a single file on disk, making it lightweight and easy to integrate into a wide range of applications, particularly mobile apps, desktop software, and small-scale web applications.
30 Dec, 2024
Most Frequently asked dataframe Interview Questions (2024)
A DataFrame is a two-dimensional, size-mutable, and potentially heterogeneous tabular data structure in pandas, which is a widely used data analysis and manipulation library in Python. It is similar to a table in a database or an Excel spreadsheet, where data is organized in rows and columns. Each column can hold different data types (e.g., integers, floats, strings), making it more flexible and powerful than a regular 2D array.
29 Dec, 2024
Most Frequently asked database Interview Questions (2024)
A database is an organized collection of structured data that is stored and managed electronically. It is designed to handle large volumes of information in a way that is efficient, secure, and accessible. Databases allow for the easy storage, retrieval, modification, and management of data. They are essential for applications ranging from small websites to large enterprise systems.
29 Dec, 2024
Most Frequently asked mongodb Interview Questions (2024)
MongoDB is a NoSQL, open-source, document-oriented database designed for scalability, flexibility, and high performance. Unlike traditional relational databases, MongoDB uses a flexible schema design, storing data in JSON-like documents. This approach makes it well-suited for handling unstructured or semi-structured data.
29 Dec, 2024
Most Frequently asked postgresql Interview Questions (2024)
PostgreSQL is an advanced, open-source relational database management system (RDBMS) that emphasizes extensibility, standards compliance, and scalability. It is known for its robustness, support for complex queries, and ability to handle large-scale data operations. It was initially developed in 1986 at the University of California, Berkeley, and has since become one of the most widely used databases.
27 Dec, 2024
Most Frequently asked sql-server Interview Questions (2024)
SQL Server is a relational database management system (RDBMS) developed by Microsoft. It is used to store, retrieve, and manage data in a structured format, primarily using Structured Query Language (SQL) to query and manipulate the data. SQL Server is widely used in enterprise environments for various applications, from small business applications to large-scale enterprise systems, supporting OLTP (Online Transaction Processing) as well as OLAP (Online Analytical Processing).
25 Dec, 2024