A derived table is a technique for creating a temporary set of records which can be used within another query in SQL. You can use derived tables to shorten long queries, or even just to break a complex process into logical steps.
If you’ve been writing SQL queries for a while you’re probably fairly confident with writing single SELECT statements to return a set of records. If you’re ready for a bit more of a challenge, this blog will teach you how to nest one SELECT statement inside another in order to create a subquery. If you’re thinking “that sounds simple enough” then you might want to read to the end of this series, where we’ll attempt to melt your brain by explaining correlated subqueries!
This article provides a comprehensive tutorial in Microsoft SQL Server, taking you from the basics of writing SELECT statements all the way through to creating complex stored procedures.
This blog gives training on writing CTEs in SQL, or Common Table Expressions to give them their full title. The blog also includes a section on creating recursive CTEs.