SQL Server User-Defined Functions

User-Defined Functions (UDFs) are an essential part of the database developers' armoury. They are extraordinarily versatile, but just because you can even use scalar UDFs in WHERE clauses, computed columns and check constraints doesn't mean that you should. Multi-statement UDFs come at a cost and it is good to understand all the restrictions and potential drawbacks. Phil Factor gives an overview of User-defined functions: their virtues, vices and their syntax.

Simple SQL: Attribute Splitting

If the design of a relational database is wrong, no amount of clever DML SQL will make it work well. Dr. Codd’s Information Principle is that you have, inside the entity tables, the columns that model the attributes of that entity. The columns contain scalar values. Tables that model relationships can have attributes, but they must have references to entities in the schema. You split those attributes at your peril. Joe Celko explains the basics.

The Missing Price

TRY_CONVERT and IsNumeric

Dropping PKs

Dynamic SQL

The Basics of Good T-SQL Coding Style

TSQL Code must work properly and efficiently. That's not enough though. Unless you are working alone, have perfect memory and plan to never change job, then you need to comment and document your code, it must be inherently readable, well laid out, use informative and obvious names, and it must be robust and resilient; written defensively. It must not rely on deprecated features of SQL Server, or assume particular database settings. Robert Sheldon starts a series of articles that explains the basics.

@@rowcount and the OUTPUT clause

OUTPUT clause with an update

Use T-SQL to Find Folders Using the Most Disk Space

Your SQL Server drives are running out of disk space and you want a way to quickly tell which sub-directories are taking the most space - here's how to do it with T-SQL.