Progress
DataServer for
Microsoft SQL Server
Guide


Unknown Values

The DataServer supports null values. Procedures that use a null value behave exactly as they do when accessing an unknown value ("?") in a Progress database, except for one difference—you cannot compare a field to the unknown value if the field is not allowed to hold the unknown value (i.e., is not null-capable). For example, if the cust-num field is not null-capable, the following statement fails at run time:

FIND cust WHERE cust-num <> ? 

A column that is not null-capable is marked “mandatory” in the schema holder.

In a DataServer application, you assign the unknown value to a column by using the question mark operator (?), which the DataServer translates to the appropriate null-value representation. For example, the following procedure assigns the unknown value to the address2 field of the customer table:

FIND FIRST customer.
address2 = ?. 


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