Introduction to SQL

A practical SQL reference built from real questions and answers. Covers SELECT, joins, GROUP BY, subqueries, window functions, indexes, transactions, and stored procedures with short, ready to run examples.

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A vendor-neutral course on standard SQL. It starts with the relational model and moves through CREATE TABLE, data types, SELECT, joins, grouping, NULL handling, transactions, and views.

Wikibooks

More than 280 pages of T-SQL tips. Topics include data types, common table expressions, window functions, JSON and XML handling, indexes, stored procedures, triggers, and backup and restore.

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A hands-on reference for SQL in Oracle. It covers joins, hierarchical queries, string and date functions, sequences, partitioning, indexes, and the basics of PL/SQL.

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