The UPDATE statement identifies an existing
access descriptor or
view descriptor that you want to change. The descriptor can exist in a temporary (WORK) or permanent
SAS library. If the descriptor has been protected with a SAS password that prohibits editing
of the access or view descriptor, then the password must be specified in the UPDATE
statement.
To update a descriptor, use its three-level name. The first level identifies the
libref of the library where you stored the descriptor. The second level is the descriptor's
member name. The third level is the
type of
SAS file: ACCESS or VIEW. For a view descriptor, you can specify the PSBNAME and PCBINDEX
arguments.
You can use the UPDATE
statement as many times as necessary in one procedure. Use these guidelines
to write the UPDATE statement:
-
Like the CREATE statement, the UPDATE statement should immediately follow PROC ACCESS
and precede any
database definition and editing statements. Also, all database definition statements should
precede any editing statements.
-
Within the database definition group, the DELETE, INSERT, and REPLACE statements can
be specified in
any order and can occur multiple times with an UPDATE sequence. The order has no effect
on processing.
-
When using
index numbers, the numbers specified with the UPDATE statement refer to the original pre-update
order. Index numbers used with editing statements always apply to the post-update,
“ready to rewrite” order.
-
Use the LIST statement after the UPDATE statement and avoid using intermediate LIST
statements, particularly in
batch mode. The LIST statement forces a reorganization of the in-memory layout of the access
or view descriptor. Intermediate list statements change the index numbering at each
invocation and can cause an error.
-
Do not attempt to create a view descriptor after you have updated a view descriptor
in the same procedure execution. You can
create a view descriptor after updating or creating an access descriptor or after
creating a view descriptor.
The following examples edit the access descriptor IMSLIB.CUSTS. Despite the order
of the INSERT, DELETE, and REPLACE statements in
the update sequence, the examples produce identical results.
/* ----example 1------ */
proc access dbms=ims;
update imslib.custs.access;
insert address;
item=address2 lv=3 dbf=$12 se=custadd2;
delete contact;
repl 23 se=custphon;
ins 23;
item=newitem lv=3 dbf=$30 se=custlsti;
run;
/* ---example 2--- */
proc access dbms=ims;
update imslib.custs.access;
delete contact;
repl 23 se=custphon;
ins 23;
item=newitem lv=3 dbf=$30 se=custlsti;
insert address;
item=address2 lv=3 dbf=$12 se=custadd2;
run; The following example shows how index numbers are interpreted by different parts
of an UPDATE statement. In the example,
the DELETE statement processes the third item in the original descriptor. The DROP
statement, however, processes the fourth item in the post-update order, which in this
case would have been the fifth item in the original sequence.
proc access dbms=ims;
update imslib.custs.access;
delete 3; /* pre-update item 3 */
drop 4; /* post-update item 4 */
list all;
run; Pre-update and post-update
listings are shown below.
/* ---prior to UPDATE --- */
IMS Database: CUSTOMER
Function: Create Descriptors-access: CUSTS1 view:
L# Item Name DBFormat Format
1 01 CUSTOMER *RECORD* *RECORD*
2 02 CUSTOMER-INFO *GROUP* *GROUP*
3 03 CUSTOMER-CODE $8. $8.
4 03 STATE $2. $2.
5 03 ZIP 10.0 12.0
6 03 COUNTRY $20. $20.
/* ---after UPDATE --- */
IMS Database: CUSTOMER
Function: Create Descriptors-access: CUSTS1 view:
L# Item Name DBFormat Format
1 01 CUSTOMER *RECORD* *RECORD*
2 02 CUSTOMER-INFO *GROUP* *GROUP*
3 03 STATE $2. $2.
4 03 ZIP *NON-DISPLAY* 10.0 12.0
5 03 COUNTRY $20. $20.