Then what's wrong with the original format you used for the query?

Do you mean it's stored as plain text in that format and not a datetime?

What exactly are you doing with the files?  If you're just streaming them into a database it shouldn't matter.

You shouldn't be able to add that constraint at all with the sample data you provided because the first record will already violate it.  Or if the constraint is already...

Or the evil of people who hide columns/rows :crazy: 

It sounds like you just need some kind of error trapping in your power shell script, it's a scripting language so it'll happily continue after an error.  Try taking a...