We had the Top 5 wishes for MySQL started by Jay recently. So in true chain letter fashion I’m starting a new one this week. “The top 5 Best Practices for MySQL”. This like it’s predecessor is generally vague, so it can include points on development, design, administration etc.

My list:

1. Write your application to support Transactions (and therefore use a Transactional Storage Engine).

2. Always use SQL_MODE. e.g. at least TRADITIONAL and ANSI to ensure better data integrity and errors as errors.

3. Use the most optimal data types (particularly for number (e.g. TINY/SMALL/BIG INT and nullability) and especially in relation to columns in indexes.

4. When using InnoDB use the shortest primary key possible (e.g. INT UNSIGNED. BIGINT unless you have more then 4 billion rows in your potential data set is laziness).

5. VARCHAR(255) is just plain dumb and lazy. This is not database design and for the record, yes there is an impact when your queries use certain buffers (e.g. sort_buffer). Last year I wrote on this topic in If you don’t know your data, you don’t know your application.. Combined with SELECT * FROM TABLE in queries is not a well designed application.

Obviously I need to clarify that this is a baseline for Best Practice and many considerations can lead to a more optimized means depending on circumstances, for example using MyISAM or other MySQL non-transactional storage engines etc, when not to use sql_mode etc and when the shortest Innodb is not the best when you are being killed by I/O. For points 3 and 5, there are no exceptions.

To all Planet MySQL bloggers and readers, the challenge is on.