<> not equal not working

[monfas]

Hi, I have the an update query that should be looking for records in one field that are not equal to a txt box (txtMovID) and replace them for the value that is in the text box - updating the new MovID in the table.

My criteria is:

<>[Forms]![fManifest]![MovID] - 'this is to say to look for any value that doesn't match the MovID text box.

This was working fine, but now (and I have no idea why) it will only update records where the value is not null and different from the txtMovID value, so if the record is null in that field (if the field is empty), even though different from txtMovID, the update query will not update it.

What might have happened here to access stop recognizing Null as not equal?

Thanks

 

[John Big Booty]

Perhaps your records where previously holding a Zero Length String (ZLS), rather than a Null value.

To account for Null values simply add Or Is Null to your criteria.

 

[ChrisO]

Null, in a general sense in Access, equates to ‘unknown’.

An ‘unknown’ is regarded as false even though an ‘unknown’ can not be said to False.

Null = anything is regarded as false.
Null <> anything is also regarded as false.
Null = Null is also regarded as false.

When an ‘unknown’ is compared to anything, even another ‘unknown’ the result can not be regarded as true and therefore must be regarded as false.

Chris.

 

[monfas]

Thanks guys,

This makes sense now. I will fix it