Null microsoft access

This is because any expression containing a N ull is itself Null and, therefore, False. For more information about working with VBA, select Developer Reference in the drop-down list next to Search and enter one or more terms in the search box. This example uses the IsNull function to determine if a variable contains a Null.

Popular functions. Need more help? Expand your skills. Get new features first. Was this information helpful? Yes No. Thank you! Any more feedback? Susan Sales Harkins is an IT consultant, specializing in desktop solutions.

Previously, she was editor in chief for The Cobb Group, the world's largest publisher of technical journals. Null values are an enigma to some and, as a result, are often handled badly by even the best IT pros. Few of us can totally escape the errors that pop up when null entries work their way into the application unexpectedly.

Perhaps the best way to handle null entries is to avoid them altogether, but that isn't always possible. Null values are valid in some cases, and when an application must accommodate them, you need to make sure Access finds them. The errors that result from improperly handled null entries aren't always obvious and can show up later as erroneous data.

By then, you may have trouble tracking the problem. Defining null It's easy to think of null and blank entries as the same thing, but they aren't equal. That's not the same as saying the data doesn't exist, although it may not.

Often, null entries are an indication that the value will be forthcoming or that someone is still searching for the data.

For example, a customer may have several phone numbers, but your user may not know the fax number when he creates the new record. The Nz function takes two arguments. The first's a value usually a query field that may contain a null value. The second parameter's the value that you want to show in the query results if Access finds a null value. Here's an example that uses Nz to convert null values in the Quantity field to Converting to 0 is actually the standard behavior of Nz , so you can leave off the second parameter if that's what you want:.

At this point, you may not be terribly impressed at the prospect of changing blank values in your datasheet into zeroes. But this function's a lifesaver if you need to create calculated fields that work with values that could be null.

Consider this innocent-seeming example:. This expression runs into trouble if Quantity is null. Nulls have a strange way of spreading, somewhat like an invasive fungus.