MySQL Tutorial - W3Schools
Learn MySQL MySQL is a widely used relational database management system (RDBMS). MySQL is free and open-source. MySQL is ideal for both small and large applications. Start …
MySQL SUBSTR () Function - W3Schools
SELECT SUBSTR ("SQL Tutorial", -5, 5) AS ExtractString; Try it Yourself » Previous MySQL Functions Next
MySQL PRIMARY KEY Constraint - W3Schools
MySQL PRIMARY KEY Constraint The PRIMARY KEY constraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values. A …
PostgreSQL - pgAdmin 4 - W3Schools
Connect to the Database In the previous chapter we learned how to connect to the database using the SQL Shell (psql) application, which is a command-based application that allows us to …
SQL Injection - W3Schools
SQL Injection SQL injection is a code injection technique that might destroy your database. SQL injection is one of the most common web hacking techniques. SQL injection is the placement …
MySQL Examples - W3Schools
MySQL Joins INNER JOIN - Join two tables INNER JOIN - Join three tables LEFT JOIN RIGHT JOIN CROSS JOIN Self Join Examples Explained
PHP Tutorial - W3Schools
Learn PHP with W3Schools, a comprehensive tutorial featuring examples and an online editor to help you master PHP programming.
MySQL FOREIGN KEY Constraint - W3Schools
MySQL FOREIGN KEY Constraint The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables. A FOREIGN KEY is a field (or collection of fields) in one …
XML Schema How To - W3Schools
Learn how to create and use XML Schema Definitions (XSD) with step-by-step guidance and examples on W3Schools.
SQL INNER JOIN - W3Schools
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