SQL Encryption Functions
There are two ways of securing data in a database: hashing and encryption. Hashing usually prevents you from obtaining the original string. Encryption allows you to obtain the original string (through decrypting). This is only possible if you know the encryption method, and the key that was used to encrypt it.

SQL Functions - String Functions
SQL provides a large amount of functions for string manipulations. Learn how to convert and use SQL Functions.

SQL Functions - Math Functions
Just like how programming languages have functions built-in to allow you to do common tasks easily. So does SQL. A lot of these functions are mathematical. Some of them are more useful than others.

SQL Date Functions - Converting and Using
SQL provides a lot of functions for manipulating dates in a database. You can store values in a date field or a datetime field. If you store the dates as unix_timestamps you can get a lot more flexibility with dates. In fact, this is usually what is done when you are using PHP with the database.

Writing SELECT queries for SQL databases
When you want to get results from a database you issue a select query. With this query you can limit the results based on certain criteria, sort it, and subsort it. You can do a lot with this including selecting data from multiple tables.

How to Fight Spam in Forums
How to Fight Spam in Forums like phpbb and Vbulletin

MySQL FAQs - SQL SELECT Statements with JOIN and Subqueries
A collection of 16 FAQs on MySQL SELECT statements with JOIN and subqueries. Clear answers are provided with tutorial exercises on joining multiple tables with inner and outer joins; using subqueries with IN, EXISTS, and FROM clauses; using UNION operations.

Creating Calculated Fields
In this tutorial, you will learn what calculated fields are, how to create them, and how to use aliases to refer to them from within your application.