Databases & SQL
Relational and non-relational models, and the SQL clauses that actually run against them.
About this track
SQL is declarative, which is exactly why it is hard to learn: you write what you want and the engine decides how. These pages show the how. Run a join and watch rows pair up; run a GROUP BY and watch rows collapse into one.
The track covers the relational model and its NoSQL alternative, then works through the clauses in the order a query is actually evaluated, ending on window functions and CTEs.
All 12 modules, in teaching order
- 01What are Relational Databases?Interactive introduction to relational databases - primary keys, foreign keys, normalisation and the update anomalies that flat tables cause.
- 02What are Non Relational Databases?Interactive NoSQL lab - compare document, key-value, column-family and graph databases against a relational model of the same data.
- 03Datatypes in SQLInteractive SQL datatypes lab - integer ranges and overflow, CHAR vs VARCHAR storage, FLOAT vs DECIMAL precision loss, dates and NULL.
- 04DDL in SQLInteractive DDL lab - build a table with CREATE TABLE, apply ALTER, TRUNCATE and DROP, and see the effect on schema and data.
- 05DML in SQLInteractive DML lab - run INSERT, UPDATE, DELETE and SELECT against a live table, see affected rows highlighted, and practise COMMIT and ROLLBACK.
- 06Where Clause in SQLInteractive SQL WHERE clause lab with a real predicate parser - comparisons, AND OR NOT, IN, BETWEEN, LIKE and NULL handling evaluated live.
- 07Limit and Offset in SQLInteractive SQL LIMIT and OFFSET lab - page through results, see why ORDER BY is mandatory, and understand the cost of deep offsets.
- 08SQL GroupBy VisualizerGroup rows by a column and watch COUNT, SUM and AVG collapse many rows into one row per group, live against a sample table.
- 09SQL Joins VisualizerWatch INNER, LEFT, RIGHT and FULL joins pull rows from two tables, and see exactly which rows each variant keeps.
- 10Common Table Expressions in SQLInteractive SQL CTE lab - see how WITH clauses turn nested subqueries into readable pipelines, and step through a recursive CTE iteration by iteration.
- 11SQL Window FunctionsRank, total and compare across rows without collapsing them, using OVER and PARTITION BY on a live result set.
- 12Regular Expressions in SQLInteractive SQL regular expression lab - test REGEXP patterns live against table rows and compare them with LIKE pattern matching.