| SAS/ACCESS Interface To ADABAS: Reference |
When the interface view engine is
reading
ADABAS data and constructing an observation, it could find missing (null) values for data fields within an observation.
The interface
view engine uses the L1, L2, L3, and L4 commands to retrieve ADABAS data. The values are returned in the record buffer using the standard length and format
defined for that field. (Standard length is not used if you have specified a value for the DB Content field or the field is a variable length field.) If the field's value is null, the data are
returned in the format in effect for that field.
Formats and their corresponding null values are listed below.
When
an
ADABAS record is read, the interface view engine is unable to tell whether a field has a value of zero (for numeric fields) or blanks (for alphanumeric fields)
or truly has a null value. This is also true when you are updating. When you are using the FSEDIT procedure, if a value of zero or missing is used to modify an existing record, zeros are placed in
the ADABAS record buffer and subsequently added
to the ADABAS file. Blanks are placed in the record buffer if a blank or missing value was supplied for an alphanumeric field.
Since
SAS System missing values are stored as zeros and blanks in ADABAS files, some SAS WHERE clauses are also impacted. For example, if either of the following SAS
WHERE clauses are issued,
where aa is missing;
where aa is null;
the resulting condition is sent to ADABAS:
where aa = 0 (numeric)
where aa = '∅' (alphanumeric)
Note:
Null values are processed differently by ADABAS if the ADABAS descriptor used in a WHERE
clause has the Null Value Suppress (NU) definition option defined for it. ![[cautend]](../common/images/cautend.gif)
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
