Joining a table stored within a column of the results

Question

I want to try and keep this as one query and not use PHP, but it's proving to be tough.

I have a table called applications, that stores all the applications and some basic information about them. Then, I have a table with all the types of applications in it, and that table contains a reference to another table which stores more specific data about the specific type of application in question.

select applications.id as appid, applications.category, type.title as type, type.id as tid, type.valuefld, type.tablename
from applications
left join type on applications.typeid=type.id
left join department on type.deptid=department.id
where not isnull(work_cat)
and  work_cat != ''
and applications.deleted=0
and datei between '10-04-14' and '11-04-14'
order by type, work_cat

Now, in the old version, there is another query on every single result. Over hundreds of results... that sucks.

This is the query I'd like to integrate so I can get all the data in one result row. (Old is ASP, I'm re-writing it in PHP)

query = "select sum("&adors.fields("valuefld")&") as cost, description from "&adors.fields("tablename")&" where appid = '"&adors.fields("tablename")&"'"

Prepared statements, I'm aware, are the best solution, but for now they are not an option.

Answer 1

You can't do this with a plain SQL query - you need to have a defined set of tables that your query is based on. The fact that your current implementation queries from whatever table is named by tablename from the first result-set means that to get this all in one query, you will have to restructure your data. You have to know what tables you're querying from rather than having it dynamic.

If the reason for these different tables is the different information stored in each requiring different record (column) structures, you might want to look into Key/Value pair storage in a large table. Once you combine the dynamically named ones into a single location you can integrate your two queries together.