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:

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
  1. The unknown packed decimal value causes errors when other languages, such as RPG, access it.

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.

Table B–2: Legacy Unknown Value Defaults for DB2/400 Date Formats 
DB2/400 Storage Format
Unknown Value
*EUR
31.12.9999
*ISO
9999-12-31
*JIS
9999-12-31
*USA
12/31/9999
*DMY
31/12/99
*MDY
12/31/99
*YMD
99/12/31
*JUL
99/365


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