How do I search for data in a column and include NULL values?
In standard SQL, a field with nothing in it (i.e. NULL) can match no retrieve profile except WHERE FIELD IS NULL. A null value in the field means that the value is unknown and therefore cannot match any comparison. This is known as `three-valued logic’. Consider the following retrieve profile: …WHERE FIELD = ‘XXX’ Typically, this retrieve profile assumes that the user does not want to retrieve records in which FIELD is NULL (in user terminology, the `empty entries’). If your application requires that the NULLs be retrieved, use the Uniface profile characters. The equal sign “=” on its own means IS NULL and the vertical bar “|” means OR. Take the value entered by the user and append “|=” to it, and Uniface will add OR FIELD IS NULL to the generated SQL.
