Question

I’m getting the following data from a MySQL database

    +----------------+------------+---------------------+----------+
    | account_number | total_paid | doc_date            | doc_type |
    +----------------+------------+---------------------+----------+
    |             18 |    54.0700 | 2009-10-22 02:37:09 | IN       |
    |            425 |    49.9500 | 2009-10-22 02:31:47 | PO       |
    +----------------+------------+---------------------+----------+

The query is fine and I’m getting the data I need except that the doc_type isn’t very human readable. To fix this, I’ve done the following

CREATE TEMPORARY TABLE doc_type (id char(2), string varchar(60));
INSERT INTO doc_type VALUES 
 ('IN', 'Invoice'),
 ('PO', 'Online payment'),
 ('PF', 'Offline payment'),
 ('CA', 'Credit adjustment'),
 ('DA', 'Debit adjustment'),
 ('OR', 'Order'); 

I then add a join against this temporary table so my doc_type column is easier to read which looks like this

+----------------+------------+---------------------+----------------+
| account_number | total_paid | doc_date            | document_type  |
+----------------+------------+---------------------+----------------+
|             18 |    54.0700 | 2009-10-22 02:37:09 | Invoice        |
|            425 |    49.9500 | 2009-10-22 02:31:47 | Online payment |
+----------------+------------+---------------------+----------------+

Is this the best way to do this? Is it possible to replace the text in one query? I started looking at if statements but it doesn’t seem to be what I’m after or maybe I just read it incorrectly.

// EDIT //

Thanks everyone. I suppose I’ll keep doing it this way.

Unfortunately, it’s not possible to change doc_type to integer as this is an existing database for a billing application I didn’t write. I’d end up breaking functionality if I made any changes other than adding a table here and there.

Also appreciate the easy to understand case statement from Rahul. May come in handy later.

Answer 1

Your current way is the best. Arguably, document_type can be changed to an int, to save space and whatnot, but that’s irrelevant.

Doing the join will be much faster and readable than any chained ifs.

Not to mention, extensible. Should you need to add a new doc_type, it’s just an insert vs. potentially several queries.