Read this SQL tutorial to learn when to use SELECT, JOIN, subselects and UNION to access multiple tables with a single statement. It’s sometimes difficult to know which SQL syntax to use when ...

Learn how to master the SELECT statement to form truly useful data queries. This article explains functions, clauses, and keywords that will make your life a lot easier.

DB2, Microsoft SQL Server, Oracle and PostgreSQL all support recursive queries using CTEs. Note that Oracle also offers an alternative syntax using the CONNECT BY construct, which we will not discuss ...