I know a lot of developers like using UUID's for primary keys instead of integers. But one thing I see alot is the use of the varchar datatype to store these strings.

If your using ColdFusion's CreateUUID() function to generate a unique identifier, you will notice that it always returns a 35 character string. So why store it in a variable length column in the database? Instead of using varchar (35) you can simply use char (35).

As a rule, if you are storing a fixed length string in a database use char rather than varchar. A varchar will have an extra byte of overhead on most databases (usually an integer stating the actual length of the string).

Some other common places where you should use char over a varchar include:

• Two Character US State Codes
• Two Character Country Codes
• One Character Status Flags