For numeric fields, you could use a default value of 0, but that might cause trouble in the long run because functions handle Null and 0 differently see 7. In addition, the Default property works only for new records. That means that you can't apply this solution to existing records. The truth is, it's usually easier to handle null values than it is to usurp them in this fashion. Don't try to find null values by equating them to anything else. The following expressions return an error, regardless of anything 's value:.
As far as Access is concerned, Null doesn't equal anything. This isn't always true outside Access. Once you decide that null values are acceptable, it's your job to accommodate them throughout the application. For instance, to find null values in a query, you'd enter Is Null in the appropriate field's Criteria cell. For instance, the use of IsNull in the following If statement handles a potential runtime error when null values exist:.
Access won't always work with null values as you might expect. If you allow them, be prepared for surprises. For instance, a simple expression such as. Instead of returning just the Subtotal, as you might expect, the expression returns Null. That's because any equation that encounters a null value will always return Null.
Although it's a nuisance, it makes sense. You can't evaluate an unknown value. If your data contains null values, use the Nz function to protect your expressions from this error. Specifically, Nz returns a value other than Null when it encounters Null as follows:. In this case, Nz returns 0 when Shipping equals Null. Use Nz in criteria and VBA expressions.
Access projects don't support Nz. Fortunately, there's an oddly named tool for just this task: the Nz function. 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.
Ask a question. Quick access. Search related threads. Remove From My Forums. Answered by:. Archived Forums. Sign in to vote. User posted Ok, I'm struggling here a bit trying to figure out how to go about inserting null value into a number field in MS Access using C. Wednesday, November 26, AM. User posted The following will convert the value to a string and attempt to convert it to an int.
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