Question

I have a master table (hereafter called SURVEY) and a detail table (hereafter called ANSWERS.) Unsurprisingly, ANSWERS has answers to SURVEY questions. ANSWERS has a VARCHAR2 column named TEXT. Some ANSWERS.TEXT values are truly text but some are actually numerics. Fortunately, I always know which rows contain text and which contain numbers-as-text.

This is the way it is. I can’t change this.

Back in the day, when certain ANSWERS rows were saved, their TEXT values were cherry-picked and put into the SURVEY table in properly typed columns. A trivial one-table select would fetch SURVEYs and the special values.

But now, with the addition of a new application, we’ve removed the special columns. Instead, we now have to fetch the appropriate ANSWERS rows’ TEXT values instead.

I have created a query that simulates the old trivial select statement. It works great… mostly.

Here’s a snippet:

select survey.*, 
       j2.overall_score
  from survey,
       (select to_number(trim(ANSWER.text)) overall_score, 
               survey.id survey_id 
          from ANSWER, 
               [edited - more SQL that gets the 'score' row from ANSWERS]) j2      
 where
   survey.id=j2.survey_id
   and overall_score > 70    

You might note the j2. In the real query, there are six such columns, j1 through j6. When I run the query, it looks just like the old query. You can’t tell it’s really being assembled from a master/detail. That’s a relief!

My problem, however, is that the ‘overall_score > 70’ phrase causes a ‘1722 invalid number’ error. Oracle is as happy as a clam when I don’t include the phrase, so all the output is passing through j2’s to_number() function and looks good. But if I add the conditional, I fail.

The ‘overall_score’ part of the where clause is being added dynamically based upon search criteria entered from a web page.

I need some fu that tells Oracle I really do know what I’m doing, please do it. If there is non-numeric data, ok, let j2’s to_number() fail. Cool. But otherwise, just do it.

Any wise words? I’m a contractor and time is nearly up. This is a new requirement :-/

Answer 1

We created a special version of to_number which internally catches the ‘1722 invalid number’ exception and returns 0 instead of. Replacing to_number with this new function in th sql eliminated this problem for us.