MySQL Tutorials - Table Column Types for Different Types of Values
This provides tutorial notes on table column types. Topics include column types for character strings, bit strings, exact numbers, approximate numbers, data and time values.

Using SELECT to retrieve data
This tutorial deeply covers the SELECT statement of the T-SQL/SQL language. Starts from the basics - how to retrieve the values inside a column to ordering data, selecting multiple columns and then tables, joining them...

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.