Category: SQL Tutorial

Here is a clear, practical, and complete guide to the SQL CHECK constraint, including syntax, examples, engine differences, common pitfalls, and best-practice usage. ✅ What the CHECK Constraint Does A CHECK constraint enforces a...

Here is a clear, practical, and complete guide to the SQL FOREIGN KEY constraint, with examples, engine differences, and best-practice recommendations. ✅ What a FOREIGN KEY Does A FOREIGN KEY enforces referential integrity between...

Here is a clear, practical, and complete guide to the SQL PRIMARY KEY constraint, including syntax, examples, rules, and differences across major SQL engines. ✅ What the PRIMARY KEY Constraint Does A PRIMARY KEY...

Here is a clear, practical, and complete guide to the SQL UNIQUE constraint, including syntax, examples, engine differences, and best practices. ✅ What the UNIQUE Constraint Does A UNIQUE constraint ensures that all values...

Here is a clear, practical, and complete guide to the SQL NOT NULL constraint, including behavior, examples, and engine differences. ✅ What the NOT NULL Constraint Does NOT NULL ensures that a column cannot...

Here is a clear, practical, and complete guide to the SQL ALTER TABLE statement, including examples for MySQL, PostgreSQL, SQL Server, and Oracle. ✅ What ALTER TABLE Does ALTER TABLE modifies the structure of...

Here is a clear, safe, and practical guide to the SQL DROP TABLE statement, with examples for major SQL engines and important warnings. ⚠️ WARNING: What DROP TABLE Does DROP TABLE permanently deletes a...

Here is a clear, complete, and practical guide to the SQL CREATE TABLE statement, with examples for MySQL, PostgreSQL, SQL Server, and Oracle. ✅ What CREATE TABLE Does CREATE TABLE creates a new table...

Here is a clear, practical, and DBA-friendly guide to the SQL BACKUP DATABASE command, including syntax for SQL Server, MySQL, PostgreSQL, and Oracle. ✅ What BACKUP DATABASE Does A database backup creates a copy...

Here is a clear, safe, and practical guide to the SQL DROP DATABASE statement, including syntax for major database engines and important warnings. ⚠️ WARNING: What DROP DATABASE Does DROP DATABASE permanently deletes the...