Category: SQL Database

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 SQL 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 SQL 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 SQL 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 SQL ALTER TABLE statement Does ALTER TABLE modifies the structure...

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 SQL DROP TABLE Statement Does DROP TABLE permanently deletes...

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

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 SQL BACKUP DATABASE Does A database backup creates a copy of...

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 SQL DROP DATABASE Does DROP DATABASE permanently deletes the entire...

Here is a clear and practical guide to the SQL CREATE DATABASE statement, with syntax for MySQL, PostgreSQL, SQL Server, and Oracle. What SQL CREATE DATABASE Does CREATE DATABASE creates a new database on the...