Limiting the number of records from mysqldump?

Question

I am trying to load a small sample of records from a large database into a test database.

How do you tell mysqldump to only give you n records out of 8 million?

Answer 1

As the default order is ASC which is rarely what you want in this situation, you need to have a proper database design to make DESC work out of the box. If all your tables have ONE primary key column with the same name (natural or surrogate) you can easily dump the n latest records using:

mysqldump --opt --where="1 ORDER BY id DESC limit 1000000" --all-databases > dump.sql

This is a perfect reason to why you should always name your PK's id and avoid composite PK's, even in association tables (use surrogate keys instead).