Question

I have a special data environment where I need to be returned data in a certain way to populate a table.

This is my current query:

SELECT 
  bs_id, 
  IF(bs_board = 0, 'All Boards', (SELECT b_name FROM certboards WHERE b_id IN (REPLACE(bs_board, ';', ',')))) AS board 
FROM boardsubs

As you can see I have an if statement then a special subselect.

The reason I have this is that the field bs_board is a varchar field containing multiple row IDs like so:

1;2;6;17

So, the query like it is works fine, but it only returns the first matched b_name. I need it to return all matches. For instance in this was 1;2 it should return two boards Board 1 and Board 2 in the same column. Later I can deal with adding a <br> in between each result.

But the problem I am dealing with is that it has to come back in a single column both name, or all names since the field can contain as many as the original editor selected.

Answer 1

This will not work the way you’re thinking it will work.

Let’s say bs_board is '1;2;3'

In your query, REPLACE(bs_board, ';', ',') will resolve to '1,2,3', which is a single literal string. This makes your final subquery:

SELECT b_name FROM certboards WHERE b_id IN ('1,2,3')

which is equivalent to:

SELECT b_name FROM certboards WHERE b_id = '1,2,3'

The most correct solution to the problem is to normalize your database. Your current system or storing multiple values in a single field is exactly what you should never do with an RDBMS, and this is exactly why. The database is not designed to handle this kind of field. You should have a separate table with one row for each bs_board, and then JOIN the tables.

There are no good solutions to this problem. It’s a fundamental schema design flaw. The easiest way around it is to fix it with application logic. First you run:

SELECT bs_id, bs_board FROM boardsubs

From there you parse the bs_board field in your application logic and build the actual query you want to run:

SELECT bs_id, 
  IF(bs_board = 0, 'All Boards', (SELECT b_name FROM certboards WHERE b_id IN (<InsertedStringHere>) AS board 
FROM boardsubs

There are other ways around the problem, but you will have problems with sorting order, matching, and numerous other problems. The best solution is to add a table and move this multi-valued field to that table.