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Where a "summary" style report is to be produced, and a relatively small number of summary records are to be printed (ie: less than 1000), then the LANSA object called a "working" list is a viable option.
In many situations, working lists save having to create additional access paths over database files (either directly via a logical file or by using the OPNQRYF option).
For example, consider the following instance where a "departmental expenditure" file called EXPEND is read:
| Panel |
|---|
| No Format |
FILE: "EXPEND" Company Department Amount Number Number Spent #COMPNO #DEPNO #AMOUNT 02 11 276.35 01 14 100.12 01 17 764.37 02 12 1945.24 01 19 89.12 02 14 568.23 01 15 375.89 etc, etc Company Department Amount etc, etc ....... |
...
To produce a summary of expenditure by company, we could first define a "working list" called #SUMMARY as follows:
...
DEFINE FIELD(#SUMCOMPNO)
...
REFFLD(#COMPNO)
...
DEFINE FIELD(#SUMAMOUNT)
...
REFFLD(#AMOUNT)
...
DEF_LIST NAME(#SUMMARY)
...
FIELDS(#SUMCOMPNO #SUMAMOUNT)
...
TYPE(*WORKING)
...
NBR_ENTRYS(50)
...
This working list can be "visualized" as a multiple occurrence structure (or array):
| Panel |
|---|
-------------------- |
| No Format |
| ---------------------------------
Entry | Company | Amount |
|------------------- ||-------------------|
001 | | | -- |
Note that this allows for 50 different companies to be processed. If we attempted to process 51, the program would fail with a very specific error message indicating that the working list is full.
Now we can read all the "departmental expenditure" records and summarize them into the list called #SUMMARY:
SELECT FIELD(
...
#COMPNO #AMOUNT) FROM_FILE(EXPEND)
LOC_
...
ENTRY IN_LIST(#SUMMARY)
...
WHERE('
...
#SUMCOMPNO =
...
#COMPNO')
IF_
...
STATUS IS(*OKAY)
CHANGE FIELD(#SUMAMOUNT)
...
TO('
...
#SUMAMOUNT +
...
#AMOUNT')
UPD_
...
ENTRY IN_LIST(#SUMMARY)
ELSE
CHANGE FIELD(#SUMCOMPNO)
...
TO(#COMPNO)
CHANGE FIELD(#SUMAMOUNT)
...
TO(#AMOUNT)
ADD_
...
ENTRY TO_LIST(#SUMMARY)
ENDIF
...
ENDSELECT | Note |
|---|
| Note: The data can be read from file EXPEND in any order. |
Next, we could sort the list to produce the summary report in company number order:
DEF_LINE NAME(#LINE01)
...
FIELDS(#SUMCOMPNO #SUMAMOUNT)
SORT_LIST NAMED(#SUMMARY)
...
BY_FIELDS(#SUMCOMPNO)
...
SELECTLIST NAMED(#SUMMARY)
PRINT LINE(#LINE01)
...
ENDSELECT
Finally, we could re-sort the list in descending order of amount spent, and produce another summary report (ie: companies ranked from highest spender to lowest spender):
DEF_LINE NAME(#LINE02)
...
FIELDS(#SUMAMOUNT #SUMCOMPNO)
SORT_LIST NAMED#SUMMARY)
...
BY_FIELDS((
...
#SUMAMOUNT *DESCEND))
...
SELECTLIST NAMED(#SUMMARY)
PRINT LINE(#LINE02)
...
ENDSELECT Some general notes about using working lists:
- Working lists are treated like database files in many ways, you can add data to them, update data already in them or clear them.
- The WHERE parameter can contain complex expressions. For instance the previous example could have used a parameter
WHERE('(
...
#SUMCOMPNO =
...
#COMPNO) *OR ((#SUMAMOUNT * 1.34)
...
<
#AMOUNT)
...
*
...
OR (
...
#SUMCOMPNO =
...
99)').
...
This is a rather nonsensical expression, but it demonstrates the power of the LOC_ENTRY command.
- The SORT_LIST command can sort the list over more than one field, and can also support ascending or descending sorting.