remove gaps in auto increment

Question

Say I have a MySQL table with an auto incrementing id field, then I insert 3 rows. Then, I delete the second row. Now the id's of the table go 1,3. Can I get MySQL to correct that and make it 1,2 without having to write a program to do so?

Answer 1

MySQL won't let you change the indexing of an Auto-Index column once it's created. What I do is delete the Auto-Index column and then add a new one with the same name, mysql will index the newly generated column with no gaps. Only do this on tables where the Auto-Index is not relevant to the rest of the data but merely used as a reference for updates and deletes.

For example I recently did just that for a table containing proverbs where the Auto-Index column was only used when I updated or deleted a proverb but I needed the Auto-Index to be sequential as the proverbs are pulled out via a random number between 1 and the count of the proverbs, having gaps in the sequence could have led to the random number pointing to a non-existant index.

HTH