Deleting
and inserting data records in a
CA-Datacom/DB table is a straightforward process for SAS as well
as for
CA-Datacom/DB. However,
several considerations are worth noting.
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When inserting a new row in SAS, you normally visualize the new data being appended
at the end of the
SAS data file. However,
CA-Datacom/DB
conventions affect the appearance of a procedure such as FSEDIT.
When you include a WHERE clause or criteria that require a Select file, the customary
SAS behavior applies. Otherwise, newly added data records appear in order by the
Native Key, not at the end. The new records are always inserted in the table in the proper
place, in order by the Native Key. Including or not including a WHERE clause simply
determines how the table looks to SAS.
Note: If you are going to use a
view descriptor to insert new data records, you must select at least
one key (or the fields that make up the key) for that view descriptor.
Select the Master Key if the Master Key values must be unique. If
you request repositioning (that is, the DDBLOAD= option is set to
zero or default to zero), either the default key must be selected
or all of the fields that it comprises must be selected. An ADD cannot
be processed if DDBLOAD equals 0 and the Default Key field is set
to blanks.
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If INCLUDE-NIL-KEY equals YES, null values are indexed. However, if DUPE-MASTER-KEY
equals NO, duplicate values cannot be indexed. That is, if you insert two records
with missing values for the
Master Key, the second insert fails. Native Key values must be unique, another reason that
the second insert of a
missing value fails.
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In order for you to even see newly added records while in an interactive procedure,
the interface view engine does some fairly complex processing that is referred to
as repositioning. Repositioning
means retrieving a record immediately after it has been inserted, so that it is visible
to you. This is important in an interactive procedure, but not as important in a
procedure such as PROC APPEND. Therefore, to save processing time, a DDBLOAD= data
set option is available that enables you to turn repositioning on and off. Setting
the
DDBLOAD= data set option causes the APPEND procedure, such as to process faster and
more efficiently. For more information about the DDBLOAD= data set option, see
Data Set Options.
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Deleting a data record removes
the record from the CA-Datacom/DB
table. The deleted data record is no longer available for access
even though it might have satisfied the WHERE clause selection criteria
before it was removed.