DBMS & SQL
Database design and SQL — ER models, normalization, joins, queries, transactions and stored procedures.
Behind every app, website and dashboard is a database. Knowing how to design one well and pull exactly the data you need with SQL is a skill that's useful in almost every tech role — and it never really goes out of date.
This hub covers both halves. The design side: what a DBMS is, the ER model, the relational model, normalization and keys. The query side: SELECT basics, INSERT/UPDATE/DELETE, joins, group by & aggregates, subqueries, views, stored procedures, triggers and transactions (ACID).
We follow the current SQL:2023 standard and practise on MySQL/PostgreSQL, and we're careful to flag where a feature is vendor-specific rather than standard SQL — a distinction most tutorials blur.
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The ER Model Explained
A plain-language guide to the Entity-Relationship model — the conceptual blueprint you draw before you build any database. Covers entities, attributes, keys, relationships, cardinality, and how to convert an ER diagram into tables.
5 min readKeys in DBMS Explained
Every type of key in a relational database explained simply: super, candidate, primary, alternate, composite, foreign, and surrogate keys — with SQL you can run.
5 min readDatabase Normalization (1NF–BCNF)
A step-by-step walk through normalization from 1NF to BCNF, using one example table refactored stage by stage. Covers functional dependencies, the anomalies normalization prevents, and when denormalization makes sense.
5 min readThe Relational Model Explained
The relational model is the theory behind every SQL database. This guide explains relations, tuples, attributes, domains, schemas, keys, and the integrity rules that keep your data consistent.
5 min readConstraints in SQL
SQL constraints are rules the database enforces on your data: NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK and DEFAULT. This guide explains each with examples and shows how they prevent bad data.
5 min readGROUP BY & Aggregate Functions
How to summarise data in SQL: aggregate functions (COUNT, SUM, AVG, MIN, MAX), grouping rows with GROUP BY, and filtering groups with HAVING — plus the rules that trip everyone up.
4 min readINSERT, UPDATE & DELETE in SQL
The three data-modification statements every developer needs: INSERT to add rows, UPDATE to change them, DELETE to remove them — with safety practices and the DELETE vs TRUNCATE distinction.
5 min readSQL Joins Explained
A clear, example-driven guide to SQL joins: INNER, LEFT, RIGHT, FULL OUTER, CROSS and SELF joins — what each returns, when to use it, and the mistakes that produce wrong row counts.
5 min readSQL SELECT Basics
The SELECT statement is how you read data from a database. This guide covers choosing columns, filtering with WHERE, sorting, DISTINCT, LIMIT, and the order SQL actually evaluates clauses in.
5 min readSubqueries in SQL
A practical guide to SQL subqueries — queries nested inside other queries. Covers scalar subqueries, IN, EXISTS, correlated subqueries, where they can appear, and when a JOIN is the better choice.
5 min readViews in SQL
What SQL views are, how to create and use them, the difference between regular (virtual) and materialized views, when views are updatable, and the trade-offs to weigh.
5 min readStored Procedures Explained
Stored procedures are reusable blocks of SQL logic stored in the database. This guide covers creating, calling, and parameterising them, the procedure-vs-function distinction, and when they help versus when application code is better.
5 min readTransactions & ACID Properties
Transactions group statements into an all-or-nothing unit. This guide explains the ACID properties, COMMIT and ROLLBACK, savepoints, and isolation levels — the foundation of reliable data changes.
5 min readTriggers in SQL
Triggers are procedural blocks that fire automatically on INSERT, UPDATE or DELETE. This guide covers BEFORE vs AFTER, row-level logic, a practical audit-log example, and the trade-offs of using triggers.
5 min readDBMS म्हणजे काय? डेटाबेस मॅनेजमेंट सिस्टमची नवशिक्यांसाठी ओळख
DBMS हे असे सॉफ्टवेअर आहे जे तुम्हाला डेटा सुरक्षितपणे साठवू, मिळवू आणि व्यवस्थापित करू देते. हे मार्गदर्शक DBMS काय करते, ते साध्या डेटाबेसपेक्षा कसे वेगळे आहे आणि नवशिक्या म्हणून भेटणारे प्रमुख प्रकार समजावून सांगते.
4 min readWhat is a DBMS? A Beginner's Guide to Database Management Systems
A DBMS is software that lets you store, retrieve, and manage data safely. This guide explains what a DBMS does, how it differs from a plain database, and the major types you will meet as a beginner.
4 min read
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