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:
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:
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