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What Does DB@ Date function return for invalid date string

The column mycolumn in table mytable is varchar(10) and has entries like 01/01/2013. However some rows have invalid data in mycolumn, e.g. 'garbage'

The following sql statement shows IsDate=1 for good dates but does not show 0 for invalid dates. What am I doing wrong?

Select mycolumn,
Date(mycolumn) as mydate,
case when Date(mycolumn) is null then 0 else 1 end as IsDate
from mytable
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rmk
Asked:
rmk
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1 Solution
 
Kent OlsenData Warehouse Architect / DBACommented:
Hi rmk,

To some extent, It'll depend on which version of DB2 you're using.  

On LUW, passing an illegal value into the DATE function throws an exception.  SQL0180N -- The syntax of the string representation of a datetime value is incorrect.


Kent
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rmkAuthor Commented:
Kent, I guess that means that I can't detect and handle the error in the SELECT statement.
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Kent OlsenData Warehouse Architect / DBACommented:
Not easily.  DB2 will allow quite a few formats, YYYYDDD, MM/DD/YYYY, integer, etc. and figure out the correct date from the string, but it expects something valid.

One often used option is to write a UDF to do the validity testing.  This allows you the flexibility to validate and/or convert a lot of date formats, even custom ones.

What date format are you expecting?  I'll be glad to whip up a UDF for you.


Kent
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Kent OlsenData Warehouse Architect / DBACommented:
Actually, you can also write a small stored procedure to do it automatically.  Write an exception handler that returns NULL for an invalid date.  Of course, the procedure might not be very flexible with regards to your needs.
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rmkAuthor Commented:
The table actually a staging table for importing data, so it can have virtually anything in the columns and all the columns are defined as varchar. I'm simply trying to determine if there is a valid date string in mycolumn.
My SELECT statement is actually a pass through query in a Microsoft Access front end. I think the easiest solution for me is going to be put that query inside a native Microsoft Access query where I can then use the VBA IsDate function on mycolumn to get what I want.
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Kent OlsenData Warehouse Architect / DBACommented:
Probably.  Though I'm not a big Access fan.  (Too much data in my world.)

SQL Server, MySQL, etc. all have date validation functions.  I'm thinking that it's time for DB2 to catch up and add them to the system repertoire.


Kent
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rmkAuthor Commented:
I've requested that this question be deleted for the following reason:

No one has provided an answer and I have found a work around
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Kent OlsenData Warehouse Architect / DBACommented:
The answer may not be what you wanted to hear, but it's the correct answer.
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rmkAuthor Commented:
I respectfully disagree. No one answered the question about what does the Date function return when it causes error SQL0180N. It has to return some value because it shows some value in the result set.
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Kent OlsenData Warehouse Architect / DBACommented:
Hi rmk,

It doesn't return anything, it throws an exception and sets the error code to SQL0180N.  

It would be up to the application's error handler to trap the error and substitute NULL (or any other desired value) and continue processing.


Kent
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