Question

I need to transfer data from one system A to system B. System A stores user ids are UUID and system B stores them as integers.

I am using MySQL select statement to retrieve and save data from System A and then transferring it across to System B. Is there an easy way to convert UUID into an integer in MySQL select statement?

Answer 1

As discussed in comments, you cannot simply turn a UUID into an integer and expect it to be unique. A UUID is 128-bits, versus INT(10) which is probably 32-bits. This means you have to ignore 96 bits, which equates to a very large number of potential collisions (around 78 octillion different UUIDs for every unique 32-bit value).

Not all is lost, because in 32 bits you can represent up to around 4 billion users and that’s probably enough. All you really need to do is map your existing UUIDs to an integer, and that’s actually quite straight-forward.

To achieve this, you can make a translation table that stores both UUID (as the primary key) and a unique integer (perhaps an auto-increment field). You can use this to map from System A to System B (and vice versa). You can put this table into either of the two databases, or you can keep it separate. Personally, I would put it into System B, because that is where the userId integer values actually make sense.