Download Dynamic Data Selection Lists in SAS/AF Programming Entries

Interactive Systems
DYNAMIC DATA SELECTION LISTS IN SAS/A~ PROGRAM SCREENS, or
"PICK TWO FROM COLUMN A AND ONE FROM COLUMN B"
John M. Rinehart
Abstract
particular chemical parameters at certain specified
sampling locations over some range of time.
SAS applications often involve reporting or
graphing a subset of data from a large database.
Generally, the user is asked to provide data selection or
screening criteria used to identify the desired subset. In
addition to fixed choices ("this year I last year", "Division
A / Division B", "sales I profits", etc.), these criteria may
be open-ended and based on actual data values contained
in one or more columns of the database ("report for these
SKU's ... H). The easiest and most reliable way to obtain
such values is to have the user select them from a list of
available values.
A simple, common (and unfriendly) approach
would be to give the user a "fill in the blank" screen to
enter range endpoints or a list of discrete values as data
screening criteria. This has many disadvantages for the
user, including remembering (or even knowing in the first
place) what data values to enter, and spelling them all
correctly. Then if a blank report is returned, there is
uncertainty: was a mistake made in entering the values, is
there no data matching these criteria, or did the
programmer screw up again?
A better solution would present the user with a
list of unique values available in the database, and allow
simple selection of one or more for use as discrete values
or range endpoints. Furthermore, if screening criteria may
be specified for more than one database column, the value
list presented for anyone column should reflect the
screening of any criteria already given for all other
columns. In this way, no values need to be remembered or
typed (especially important with long lists or esoteric
values, such as SKU's), and data coding for these
purposes is unnecessary. The user sees exactly what data
is available and knows what to expect in the output.
This paper presents one method for implementing
data selection lists in a SAS/AF program screen with SCL,
by querying the source dataset for available values. The
result is similar to the "pull-down list" or ·combo box" of
popular GUI databases. In addition, dynamic linking of
lists for multiple database columns is demonstrated, such
that the available values from one column reflect the
screening of any criteria already entered for other columns.
The Problem: Data Selection
The ultimate point of most information sYstems is
to return stored information to the user in a useful form
(report, graph, etc.) when requested. Usually, however,
only a subset of the available information is needed (or
wanted) to :fulfill any given request. So there must be
some way to apply selection or screening criteria to one or
more columns of the database to filter out the information
of interest.
A similar problem was discussed in the
Input/Output department of the second quarter 1995 issue
of Observations. the SAS Institute technical journal. The
solution given there, using structured SCL lists, is
somewhat limited. Only a single value may be selected for
each database column, and the columns must be addressed
in a fixed, hierarchical order. The technique discussed in
this paper is more flexible on these points, at the expense
of repeatedly accessing the source dataset. Multiple
discrete values may be specified for any database column,
and in any order.
Sometimes, useful subsets of information can be
anticipated in the system design, "hard-coded" into the
application, and presented to the user in a multiple choice
menu.
More often, data selection must be left more
open-ended to accommodate changing user needs and to
reflect the availability of data. For example, a user may
need to summarize inventory and sales data for a variable
range or list of SKU's , or to plot water quality results for
The sample demonstration given here uses the
following trivial source dataset with only three columns,
all used for data selection. Hopefully, extension to a real
application will be obvious, where larger source datasets
494
Interactive Systems
will have many more co1unms used for reporting after a
subset of rows is selected.
+IIUILD: DISPLAY SELECt .PJIOGRA'MM-----+
Co....and --=)
Data Selection Screen
DATASET WORK. SAMPLE
OBS
1
2
3
4
5
6
7
8
9
10
11
12
SHAPE
COLOR
SIZE
TRIANGLE
TRIANGLE
TRIANGLE
TRIANGLE
TRIANGLE
SQUARE
SQUARE
SQUARE
CIRCLE
CIRCLE
CIRCLE
CIRCLE
RED
RED
YELLOW
YELLOW
BLUE
RED
YELLOW
BLUE
RED
RED
BLUE
BLUE
1JIRGE
SMlILL
1JIRGE
SMlILL
1JIRGE
1JIRGE
1JIRGE
1JIRGE
1JIRGE
SMlILL
1JIRGE
SMlILL
--------
Shape: H1__
-
ColoI': lC1_
Size:
H2__
183 _ _
1IC2_ 1IC3_
HIZE
Ro.... selected: &ROUSEL
I
I
I
+---------------------------+
The user is instructed to leave blank all fields for
a given database column to select all available data, or to
enter screening criteria values as required. To display a
selection list of available values from which to choose, the
user will press the <ENTER> key with the cursor
positioned on a blank field. The selected values are then
copied into the window fields, as shown in this partial SCL
source code listing:
The Basic Approach
The selection list method described here is based
on a SAS/AF PROGRAM entry and SCL (screen control
language), suitable for SAS versions 6.07 and later, on
MVSITSO and other operating platforms. The method
could likely also be implemented in more recent versions
using the SAS/AF FRAME entry.
DIl:!r:
CONTROL ALWAYS
SOURCEDS = 'WORK. SAMPLE' ;
RETURN;
To display a list of values from a database
column, the SCL function DATALISTCO is used on a
temporary dataset containing the unique values. This
dataset is generated from the source dataset by SQL code
in a SUBMIT block, each time the list is displayed. The
flexibility of the SQL query used here also permits other
information to be added if needed, such as a description
field to be displayed alongside coded values in the
selection list.
MAIN:
FIELD=CURFLD();
IF (FIELD='Sl' AND Sl= BLANK) OR
(FIELD='S2' AND S2=-BLANK-) OR
(FIELD='S3' AND S3=-BLANK-)
THEN DO;
-SUBMIT CONTINUE SQL;
CREATE TABLE U SHAPE AS
SELECT UNIQUE SHAPE FROM 'SOURCEOS;
ENDSUBMIT;
DSlDooOPEN ( 'U SHAPE');
IF DSlD
THEN DO;
LIO-MruCELlST();
RC=CURLIST(LIO);
CVlIR=DATALISTC (OSlO, 'S!!APE' ,
'Select up to 3 shapes', 'N'j3);
IF GETNITEMN(LIO,'COUNT') GT 0
THEN 00;
Sl=GETNITEMC(LIO, 'SHAPE',I,l,' ')
S2=GETNITEMC(LIO, 'SHAPE',2,1,' ')
S3=GETNITEMC(LIO,'SHAPE',3,1,' ')
END;
RC=OELLIST (LIO) ;
RC=CLOSE (OSlO) ;
RC=OELETE('U SHAPE');
The DATALISTC function will display the list of
unique values (and additional descriptors) in a window,
and permit the user to select any number of them, up to a
fixed maximum. The GETNITEMC function is then used
to copy the selected values into window field variables for
review and subsequent use in subsetting the source
dataset.
Consider the following window which allows the
. user to enter data screening criteria on three columns of
the sample source dataset: SHAPE, COLOR, and SIZE.
The design allows up to three discrete values each for
SHAPE and COLOR, and only one value for SIZE. SCL
window variable names are shown in this BUll.D display:
END;
END;
495
-
Interactive Systems
determined in the system design, and set high enough to
satisfy most reasonable user needs.
Of course, other methods may be used to trigger
the selection list display, such as separate pushbutton
fields, or function keys. The displayed selection list might
look something like this:
Since the source dataset is queried each time a
selection list is requested, the system response time can be
impacted, especially for large datasets. Performance might
be improved by creating an index on the database columns
used for screening. When there are many records for each
set of values in the screening columns, response should be
snappier if the value lists are generated from a sununary
of the source dataset, containing just the unique
combinations of values, rather than the source itself:
+SAS ••••••••••••••••••••••••••••••••••••••••
Co....and ••• >
Data Select:ion Screen
Shape: _ __
+Select D a t a - - ;
Co~d =_a)
I
;
Select up to 3 ;
shape::
:
Size:
CIRCLE
SQUARE
TRIANGLE
nIl:!I!:
CONTROL ALWAYS
SOURCEDS = 'WORK. SAMPLE' ;
SUMMRYDS = 'WORK.SUMMRY';
SUBMIT CONTINUE SQL;
CREATE TABLE &S'IlMMams AS
SELECT UNIQUE SHAPE, COLOR, SIZE,
COUNT (SHAPE) AS N
FROM &SOURCEDS;
ENDSUBMIT;
RETURN;
.
;
:
*
Rows selected: 12
:
*
I
......................... +-------+
Once the user accepts the selected values with an
END key or command, they are copied back into the
window field variables, via the current environment list. If
the users CANCELs or ENDs the selection list without
selecting any values, the window fields are left unchanged.
Logically Linking Multiple Columns
+SAS----------------+
Co-..d ==->
The selection list datasets are repeatedly queried
in order to allow a dynamic logical linking of the screening
columns. In this way, each selection list includes only the
values which appear in the source dataset as already
screened on the other columns. Column relationships
might be hierarchical (e.g.- STATE > COUNTY>
CENSUSTRACT), allowing the user systematically to
reduce the size of a potentially long list, but they need not
be, as in the present example.
Data Selection Screen
Shape: SQUARE-
TRIANGLE
Colo .. : _ _
Size:
__
The linking is achieved by using the window
variable fields associated with each database column to
generate a character string which can be used as a
WHERE expression on that column. The unique value
query which generates the selection list values for a
particular column is then screened by the current WHERE
expressions for all other columns.
Rows ..elected: 8
Similar sections of conditional SCL code in the
MAIN section control the generation and display of
selection lists for the other database columns COLOR and
SIZE. Since there is only one window field for a SIZE
criterion, the DATALISTC function allows only one
selection, and can be set up to close immediately, without
the need for an END command. The maximum number of
discrete selection values for each column must be
The following partial SCL source listing shows
the WHERE expressions defined as SCL nonwindow
variables in a separate labeled section, so they can be
recalculated as needed with a LINK statement:
496
Interactive Systems
In use, column linking would look something like
this. Referring to the sample dataset listing, suppose the
user has requested triangles and squares, and has also
selected small sizes. The color selection list will be:
SLC!rYlIRS :
** Define character strings based on window
variables, to be used as WHERE
expressions when generating unique value
selection lists.**;
IF Sl!!S2!!S3 - _BLANK_
THEN SBLSBAft , (SHAPE NE "
" ) I;
+SAS ••••••••••••••••••••••••••••••••••••••••
eo..and
ELSE SBLSBAft =
'{SHAPE IN (111!IS1!!'
f
I I I t I I ! ! 53! ! I
SHAPE NE "
","'!!S2!!
r r) AND
_D_>
Data Selection Screen
II)';
Shape:
SQUR~
Size:
SIIRLL
TRIANGLE
RETURN;
JaIN:
+Select Data---+
Co_d -==)
LD1lt SLC!rYlIRS;
Select up to 3
FIELD=CURFLD ( ) ;
**Show selection list for SHAPE **;
IF (FIELD='Sl' AND 51- BLANK ) OR
(FIELD='S2' AND 52=-BLANK-) OR
(FIELD='S3' AND S3 m -BLANK-)
THEN DO;
-SUBMIT CONTINUE SQL;
CREATE TABLE U SHAPE AS
SELECT UNIQUE SHAPE FROM &50URCEDS
1IIIBRB &SELCOIoOll AlII) &SBLSIZE;
ENDSUBMIT;
cola ... :
RED
Rows se lected:
YELLOW
2
.........................+ - - - - - -
because there are no blue, sma1l, triangles or squares in the
database. For the same reason, selecting the color blue
would limit the SIZE value selection list:
+SAS ••••••••••••••••••••••••••••••••••••••••
Using the last example window, SELSHAPE
would be defined as the character string
ColllllMlRd •••>
Data Selection Screen
(SHAPE IN ('SQUARE ','1RIANGLE ',' ') AND SHAPE NE' ')
Shape:
which would be used in a WHERE clause when generating
lists of color and size values, eliminating records with
shape='CIRCLE'. Similar code is used to define variables
SELCOLOR and SELSIZE for the other screening
columns (see the complete example listing at the end of
this paper). Expressions for numeric-valued columns
would have to be defined appropriately.
SQUR~
TRIANGLE
+Select Data---+
Co..and __ a)
Size:
Select 1 size:
LARGE
Rows selected:
2
.........................+------
Because of the way these strings are used in
WHERE clauses, they must be valid WHERE expressions
even when no screening values are given ( Sl! ! S2 ! ! 53 =
_BLANKJ. The default expression used here excludes
missing values (' '), as they are also excluded when just
some of the screening value fields are left empty. Thus, it
is assumed that the database columns used for screening
contain no missing values. The technique could be
modified ifmissing·values must be included.
Likewise, first selecting juSt small objects would eliminate
squares from the SHAPE selection list, because the
database contains no sma1l squares:
497
Interactive Systems
back to the SCL window variable through a macro
variable, &ROWSEL:
+SAS ••••••••••••••••••••••••••••••••••••••••
_ eo....... ---)
Data Selection Sc.....n
MlUN:
Shape: _ __
Color:
Size:
**Determine number of rows selected**i
LINK SLCXVARS;
SUBMIT CONTINUE SQL;
RESET NOPRINT;
SELECT COUNT (SHAPE) INTO :aoNSEL
FROM &SOURCEDS
1IIIBRl!l GSELSIIAi'I: JIKD 'SELCOLOa JIKD
+Select Data--:'
Co--.nd ---)
StlALL
Select up to 3
shapes:
CIRCLE
Rows se lected:
4
TRIANGLE
'SELSlZE;
RESET PRINT;
ENDSUBMIT;
ROWSEL = SYMGETN ( •ROWSEL I )
RETURN;
......................... +------;:::: ::. , ; , ;::: I
:~ ~ ;,;:~:
".
;
On the other hand, selecting colors red and yellow will
allow all the shapes in the shape selection list, even though
Making the Final Subset
there are no yellow circles:
When the user is finally satisfied with the given
screening criteria and is ready to proceed, it is time to
make use of the values in the window variables to actually
extract the subset from the source dataset. The simplest
method is to once again submit an SQL query in the
TERM section, and create a copy of the source dataset
using the defined WHERE expressions for all of the
screening columns:
+SAS ••••••••••••••••••••••••••••••••••••••••
Co...and -==)
Data Selection Sc ....en
Shape: _ __
Color: RED_ YELLOW _ _
Size:
+Select Data--+
__
Co.....and •• ->
Select up to 3
~:
shapes:
IF STATUS NE' C' THEN
SUBMIT CONTINUE SQL;
CREATE TABLE 5StlBSETDS AS
SELECT * FROM &SOURCEDS
wm:az 'SELSDPE JIKD 5SELC:OloOa
CIRCLE
Rows selected:
8
TRIANGLE
SQUARE
......................... + - - - - - -
JIKD
5SBLSIZE;
ENDSUBMIT;
RETURN;
Counting The Results
Alternately, the values of the window variables
can be SYMPUT to macro variables in the TERM section,
to be used elsewhere in the application for subsetting the
source dataset. Either way, the selected subset is then
used to provide the user with the requested information in
a suitable form.
Careful readers may have noticed the changing
number by "Rows selected" on these examples. It
indicates the number of rows contained in a subset of the
source dataset defined by the current screening values.
This feature is another aid to the user in evaluating the
entered screening criteria and determining if the subset will
be a reasonable size. The protected field is calculated at
the end of the SCL MAIN section by submitting another
SQL query on the source dataset (or a unique value
sununary) using the WHERE expressions for all of the
screening columns. The selected record count is passed
498
Interactive Systems
Complete SCL source code for the sample selection list
application.
**Show selection list for COLOR **:
IF (FIELD='Cl' AND Cl= BLANK ) OR
(FIELD='C2' AND C2=-BLANK-) OR
(FIELD-'C3' AND C3=-BLANK-)
THEN DO:
-SUBMIT CONTINUE SQL;
CREATE TABLE U COLOR AS
SELECT UNIQUE COLOR FROM &SOURCEDS
WHERE &SELSHAPE AND &SELSIZE:
ENDSUBMIT;
DSID=OPEN('U COLOR');
IF DSID
THEN DO:
LID=MAKELIST ( ) :
RC=CURLIST (LID) :
CVAR=DATALISTC(DSID,COLOR',
lNI'1!:
CONTROL ALWAYS
SOURCEDS
'WORK.SAMPLE':
SUBSETDS = 'WORK.SUBSET':
RETURN:
SLCS'VARS:
** Define character strings based on window
variables, to be used as WHERE
expressions when generating unique value
selection lists.**;
IF Sl!!S2!!S3 = BLANK
THEN SELSHAPE-=
f
(SHAPE NE
f t
'Select up to 3 colors',N',3);
IF GETNITEMN(LID, 'COUNT') GT 0
THEN DO;
Cl=GETNITEMC(LID, 'COLOR',l,l,' '):
C2=GETNITEMC(LID,'COLOR',2,1,' ');
C3=GETNITEMC(LID, 'COLOR',3,1,' '):
I I) ';
ELSE SELSHAPE =
'(SHAPE IN ("'!!Sl!!' If,'''!!S2!!
I
I I , t , I ! ! S3! t r
I') AND
SHAPE HE "
")';
END:
RC=DELLIST (LID);
RC=CLOSE(DSID):
RC=DELETE('U COLOR'I:
END:
END;
**Show selection list for SIZE **:
IF (FIELD-'SIZE' AND SIZE= BLANK )
THEN DO:
-SUBMIT CONTINUE SQL:
CREATE TABLE U SIZE AS
SELECT UNIQUE SIZE FROM SOURCEDS
WHERE &SELSHAPE AND &SELCOLOR;
ENDSUBMIT;
DSID=OPEN('U SIZE');
IF DSID
THEN DO;
LID-Ml\KELIST();
RC-CURLIST(LID);
C~=DATALISTC(DSID, 'SIZE',
'Select 1 Size', 'Y',l);
IF GETNITEMN(LID, 'COUNT') GT 0
THEN
SIZE=GETNITEMC(LID,'SIZE',ll:
RC=DELLIST(LID):
RC=CLOSE (DSID):
RC=DELETE('U SIZE');
END:
-
IF Cl! !C2! !C3
BLANK
THEN SELCOLOR-·
, (COLOR NE "
ELSE SELCOLOR
I
I I) ';
~
I ! ! Cl ! ! r
","'!!C3!!'
(COLOR IN ("
,
COLOR NE
II
t I I
I I I
! ! C2! !
It) .AND
") I;
IF SIZE - BLANK
THEN SELSIZE ;;;
, (SIZE NE I' 't) t;
ELSE SELSIZE =
t
(SIZEa'I'! !SIZE!!
t t ') ';
RETURN:
IGIN:
LINK SLCTVARS:
FIELD-CURFLD():
**Show selection list for SHAPE **:
IF (FIELD='Sl' AND Sl- BLANK ) OR
(FIELD='S2' AND S2=-BLANK-) OR
(FIELD=' S3' AND 53=-BLANK-)
THEN DO:
-SUBMIT CONTINUE SQL;
CREATE TABLE U SHAPE AS
SELECT UNIQUE SHAPE FROM &SOURCEDS
WHERE &SELCOLOR AND &SELSIZE;
ENDSUBMIT;
DSID=OPEN('U SHAPE');
IF DSID
-
END:
**Determine number of rows selected**;
LINK SLCTVARS:
SUBMIT CONTINUE SQL:
RESET NOPRINT:
SELECT COUNT(SHAPEI INTO :ROWSEL
FROM &SOURCEDS
WHERE &SELSHAPE AND &SELCOLOR AND
&SELSIZE:
RESET PRINT;
ENDSUBMIT;
ROWSEL = SYMGETN('ROWSEL');
RETURN;
THEN DO;
LID=MAKELIST () ;
RC=CURLIST(LID):
CVAR=DArALISTC(DSID,'SHAPE',
'Select up to 3 shapes', 'N',3);
IF GETNITEMN(LID, 'COUNT'I GT 0
THEN DO;
Sl-GETNITEMC(LID, 'SHAPE',l,l,' '):
S2-GETNITEMC(LID, 'SHAPE',2,1,' 'I:
S3-GETNITEMC(LID,'SHAPE',3,1,' '):
END:
RC=DELLIST (LID) ;
RC=CLOSE (DSID);
RC=DELETE('U SHAPE'):
END;
END;
_:
IF STATUS NE 'C' THEN
SUBMIT CONTINUE SQL;
CREATE TABLE &SUBSETDS AS
SELECT * FROM &SOURCEDS
WHERE &SELSHAPE AND &SELCOLOR AND
&SELSIZE:
ENDSUBMIT:
'*'*continued**;
RETURN;
499
Interactive Systems
Summary: Pros and Cons
This technique is intended to improve user
interactions when specifYing screening criteria to define a
subset of a source dataset. It does so by allowing the user
to select from lists of available values.
Strengths:
• The user sees exactly what data values are available
in the source dataset - no guessing.
.
• Typographical errors in entering screening criteria
are avoided.
• The need for data coding as a mnemonic aid to
retrieval is eliminated.
• Value lookups may be provided to help identify
coded data.
• Data selection criteria may include multiple discrete
values for each column.
• Linking of value selection lists on multiple columns
supports "drill down" through hierarchical
relationships.
• The size of the requested subset can be reported.
Limitations:
• The source dataset (or at least a unique valued
subset) is repeatedly queried, which may affect
response time.
• Columns used for screening should not have
missing values.
• The number of discrete screening values available
to the user for each column must be hard-coded.
No technique is perfect. Learn from this what you can,
modiiY as necessary, and use to advantage.
Literature
SAS Institute, Inc., "Input/Output", Observations Second
Quarter 1995, Vol.3 No.4, pp. 63-65.
Author Contact
John M. Rinehart
3280 Skytop Trail
Dover, PA 17315
(717) 292-1636
email: [email protected]
SAS and SAS/AF are registered trademarlcs ofSAS Institute, Inc. in the
USA and other COWltries. ® indicates USA registration.
500