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| ADABAS Essentials |
ADABAS Null Values
ADABAS has a special value called a null value, which means an absence of information. A null value is analogous to a missing value in SAS.
You can define data fields not to store null data by specifying the NU option in data definition statements. In normal data storage (that is, NU not specified), a null value is represented by two bytes (one for the value length and one for the null value). Suppressing null values results in a null value being represented by a one-byte empty field indicator. The null value itself is not stored.
Knowing whether a data field has null values assists you in writing selection criteria and in entering values to update ADABAS data. For example, if the NU option is specified for an ADABAS descriptor data field, null values for the data field are not stored in the inverted list. Therefore, a search using this data field and a null value as the search value, would result in no records selected, even though there might be records that contain a null value for the data field.
For more information about null values, see Missing Values (Nulls).
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Copyright © 2007 by SAS Institute Inc., Cary, NC, USA. All rights reserved.