Lookup transform not finding blank match

I am having problems with a lookup transformation. I have a row in my lookup table for blank ('') source data. If I test the join using SQL the match is made, but the Lookup transform doesn't consider it a match and sends it to error output. Is there a property that I don't have set correctly or something else I am forgetting?

Check that you are not using empty string lookup against spaced "empty" strings or vice versa.

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I created the lookup table (dimension) and prepared the source table so I do know they are both empty strings.

Let me give a little more information. I have a package that runs prior to the fact table load (lookups). The package runs through the source and adds any dimension records that are not present. The problem arises when the lookup encounters an empty string from the source and it is unable to match on the empty string record already in the dim table, so it sends the record to the error output to be written to the dim table. But the write fails because the field is a primary key in the dim table and because the record exists it raises an error. In other words the Lookup transform can't see the empty string record, but the Write Transform can.

I hope that this explanation is understandable.

Dave

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Dave,

I've noticed when I pull back a string from tables, the string is padded with spaces to the full size of the field.

Try two things to see if one of these might be your problem:

1) After you pull in your columns from the source, add a derived column that concatenates a single character (like 'a') before and after the column that is return the empty string. Use a data viewer after this column, to see if the column looks like this: 'aa' or this 'a a'.

If it's the latter, change your derived column to trim the string, or trim the column when pulling it from the source.

2) In your initial lookup where you are trying to see if the empty string ('') exists, try using a SQL statement that selects the columns you are looking up. In your SQL statement, concatenate a single character in the same manner as step 1 to the empty string column and add it to your output. Then use a data viewer after this column to see what the column looks like.

If it's 'a a', trim your column in your SQL statement before returning it.

Good luck!

Jessica

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Like Jessica said, use the dataviewer to check the data.

SSIS is using .net string compare on strings during lookup process, which think '' and ' ' is different, but sql is ignoring trailing empty spaces during select joins.

If your oledb command insert statement check if the data exist before insert, then you may always insert ' ' into the database but always ignore the ''.

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Check out

http://blogs.conchango.com/kristianwedberg/archive/2006/02/22/2955.aspx

especially the comments at the end - you're not alone :-)

Cheers/Kristian