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📄 40 ArticlesACID Properties, Transactions, Locks, and Concurrency Control: 20 Real Interview Questions
ACID properties fundamentals define database reliability. ACID (Atomicity, Consistency, Isolation, Durability) ensures that transactions either complete fully or not at […]
SQL JOINS Fundamentals: INNER, LEFT, RIGHT, FULL OUTER JOIN Interview Guide
SQL JOINS fundamentals transform raw data into relational insights. Every analytics query involves combining data from multiple tables based on […]
SQL GROUP BY, HAVING, DISTINCT, COUNT, SUM, AVG Fundamentals
SQL GROUP BY fundamentals transform raw data into aggregated insights. Every analytics query involves grouping data by dimensions and calculating […]
SQL Window Functions: ROW_NUMBER, RANK, DENSE_RANK, LAG, LEAD Interview Guide
SQL window functions fundamentals are essential for advanced analytics and are heavily tested in senior data engineer interviews. Window functions […]
SQL Common Table Expressions (CTEs) and Recursive CTEs: Advanced Guide
SQL CTEs fundamentals (Common Table Expressions) are powerful tools for organizing complex queries. A CTE is a temporary named result […]
SQL Subqueries, Correlated Subqueries, Self-Joins, and Cross-Joins: 20 Real Interview Questions
SQL subqueries fundamentals are critical tools for complex data retrieval. Subqueries (inner queries nested within outer queries) solve problems requiring […]
SQL String Functions – SUBSTR, CONCAT, UPPER, LOWER, TRIM, REPLACE: 20 Real Interview Questions
SQL string functions fundamentals are essential for data cleaning, transformation, and validation. String functions manipulate text data: extracting substrings, combining […]
SQL Date Functions, CASE Statements, and NULL Handling: 20 Real Interview Questions
SQL date functions fundamentals enable temporal analysis essential to business intelligence. Date manipulation—calculating age, finding quarters, extracting years, computing date […]
Database Design, Normalization Forms (1NF, 2NF, 3NF, BCNF): 20 Real Interview Questions
Database normalization fundamentals form the foundation of efficient, maintainable database design. Normalization is the process of organizing data to minimize […]
Entity-Relationship (ER) Diagrams and Schema Design: 20 Real Interview Questions
Entity-Relationship (ER) model fundamentals provide a visual blueprint for database design before implementation. An ER diagram shows entities (tables), their […]