Question

Which one is better – Using mysql aggregate function COUNT to return number of selected occurrence or manually counting and inserting the count into a field during insertion operation? Considering that COUNT function searches the table or an index and groups the result, while in manual counting, I would just retrieve the field.

Answer 1

If you do it manually

• You do extra work that is not required
• You’ve to remember to do it for each insert and delete operation
• You slow down because of extra operations
• You will have inconsistencies when the table is manipulated directly
• In MyISAM table the count is already retrieved as a field by MySQL
• In InnoDB it’s a little slower, but subsequent calls are cached, so only the first one will be slow

Trying to do the work of a DBMS better than a DBMS is not a good idea. A DBMS embodies years and years of experience and optimisations.