CodeWithSQL Blog: Latest SQL Tips and Tutorials

Top SQL projects to build for your portfolio: 11 project ideas by level with schemas and example queries, plus how to present them on GitHub and where to find data.

40+ SQL interview questions and answers for 2026: joins, GROUP BY, subqueries, window functions, indexes, normalization and classic puzzles, with SQL solutions.

SQL injection explained: how the attack works, its real impact, and how to prevent it with parameterized queries, least privilege, input validation and safe coding.

How SQL indexes improve performance: how a B-tree turns scans into seeks, index vs table scan, EXPLAIN before and after, composite and covering indexes, and trade-offs.

15 SQL performance tuning tips every developer should know: indexing, sargable queries, EXPLAIN, avoiding SELECT star, pagination, batching and monitoring slow queries.

Relational database vs NoSQL: the data models, ACID vs BASE, scaling, and when to choose SQL or NoSQL (document, key-value, column, graph), with examples.

Entity relationship diagrams (ERD) explained: entities, attributes, relationships and crow foot cardinality, turning an ERD into tables, and common mistakes to avoid.

Primary key vs foreign key: what each is, how they differ, composite and surrogate keys, referential integrity, and ON DELETE and ON UPDATE actions, with examples.

How to design a relational database step by step: gather requirements, model entities and relationships, choose keys, normalize, pick data types and add constraints.

Database normalization explained: 1NF, 2NF, 3NF and BCNF walked through one worked example, the anomalies they prevent, and when it makes sense to denormalize.