Ms access where is null

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All Products. Product Awards. Forum and Ticket Submissions. Support Options. Example for Using the NZ Function. Syntax for NZ Function.

Note that when used in a query expression, the NZ function returns a zero-length string. Microsoft Access Developer Center. Excel How many simultaneous Microsoft Access users? Best Practices. Table Design. 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. Until he obtains the number or learns that the customer has no fax at all, the fax entry is null. A little background Is Null and IsNull both find null values, but you won't use them in the same way. If expression consists of more than one variable, Null in any constituent variable causes True to be returned for the entire expression.

The Null value indicates that the Variant contains no valid data. Null is not the same as Empty, which indicates that a variable has not yet been initialized. It is also not the same as a zero-length string "" , which is sometimes referred to as a null string. Important: Use the IsNull function to determine whether an expression contains a Null value. 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.

For example, say you have a table of company names and addresses. You want two queries : one that gives you the local companies, and the other that gives you all the rest. In the Criteria row under the City field of the first query , you type:.

Specify Is Null. For the second query above to meet your design goal of "all the rest", the criteria needs to be:. Maths involving a Null usually results in Null.

For example, newbies sometimes enter an expression such as this in the ControlSource property of a text box, to display the amount still payable:. The trouble is that if nothing has been paid, AmountPaid is Null, and so this text box displays nothing at all.