Changing from an enum to a linked table

Question

We are going to change something that we have an enum to an id of a linked table instead.

How would we go about that?

Our current enum name: strat
Our new linked name: stratid

What I was thinking was something along the lines of:

UPDATE table_name  
SET stratid = (SELECT id FROM link_table WHERE stratname = table_name.strat);

I have not created the link table yet, right now it is all theory.

Will the above work?
Is there anything I should change in order to transfer from an enum to the linked table?

Answer 1

No gotchas for making the update other than that you need want to make triple sure that your link_table.ids are populated strictly in the order that table_name.strat options are defined.

For example, if strat is enum('FOO', 'BAR') then in linked_table the record with id == 1 should be the "FOO" record.

After that, you 'd perhaps want to make the stratid column NON NULL; this is not strictly equivalent to your previous arrangement, but it would probably be closer to what you want.

Answer 2

Yes, create the link table first,
set the stratname as unique,
use an auto increment ID

A lazy solution for insert link_table:

insert into link_table
select distinct strat from table_name order by strat;

However, I not sure is all the predefined enum is being used.

Also, without knowing size of the enum,
I can't suggest you do a manual insert.

If you look at enum ...

enum('...', '...', ...)  <-- is just a comma separated value

So, here is the query to get the CSV :-

select column_type from information_schema.columns 
where schema_name="table_name" and column_name = "strat";

You can combine with an programming language to do the link_table insertion.

Lastly, you UPDATE query is not very optimize, you can switch to use INNER JOIN.
But I assume is one-time job, so be it!