Progress/400
Product Guide
Legacy Unknown Value
When the user does not use SQL NULL support, the Progress client translates the question mark (?) to the legacy unknown value as follows:
- When the user assigns the question mark (?) to a field, the Progress client assigns a value to the DB2/400 field based on the data type of the field. Table B–1 describes the implementation of the unknown value for each data type.
- When a Progress application retrieves a field that contains an unknown value, it returns the standard Progress unknown value (?).
Table B–1 lists the possible unknown values by data type.
Table B–1: The Legacy Unknown Value Implementation by Data Type Data Type Implementation CHARACTER A question mark (?) followed by as many blanks as necessary to fill out the field. For a field length of 1, the value is binary 255. DATE The AS/400 date data type. See Table B–2 for the unknown values for the various date formats. INTEGER 2-byte: 32,767 (the largest possible value)
4-byte: 2,147,483,647 LOGICAL A question mark (?). DECIMAL An invalid packed decimal value with an invalid sign.1
Unlike a standard Progress database, DB2/400 allows only one record with the legacy unknown value in the index field when the index is defined as a unique index.
When you load Progress DATE data that contains the unknown value (?) into OS/400 physical files, the DataServer inserts values based on the DB2/400 date format for the field. Table B–2 lists the values that the DataServer inserts.
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