4D v16.3
REDUCE SELECTION
- 4D Language Reference
-
- Selection
-
- ALL RECORDS
- APPLY TO SELECTION
- Before selection
- CREATE SELECTION FROM ARRAY
- DELETE SELECTION
- DISPLAY SELECTION
- Displayed line number
- End selection
- FIRST RECORD
- GET HIGHLIGHTED RECORDS
- GOTO SELECTED RECORD
- HIGHLIGHT RECORDS
- LAST RECORD
- MOBILE Return selection
- MODIFY SELECTION
- NEXT RECORD
- ONE RECORD SELECT
- PREVIOUS RECORD
- Records in selection
- REDUCE SELECTION
- SCAN INDEX
- Selected record number
- TRUNCATE TABLE
REDUCE SELECTION
| REDUCE SELECTION ( {aTable ;} number ) | ||||||||
| Parameter | Type | Description | ||||||
| aTable | Table |
|
Table for which to reduce the selection, or Default table, if omitted | |||||
| number | Longint |
|
Number of records to keep selected | |||||
REDUCE SELECTION creates a new selection of records for aTable. The command reduces the current selection of aTable to the first number records. REDUCE SELECTION is applied to the current selection of aTable in the current process. It changes the current selection of aTable for the current process; the first record of the new selection is the current record.
Note: If the statement REDUCE SELECTION(aTable;0) is executed, there is no longer any selection nor any current records in the table.
The following example first finds the correct statistics for a worldwide contest among the dealers in over 20 countries. For each country, the 3 best dealers who have sold product worth more than $50,000 and who are among the 100 best dealers in the world are awarded a prize. With a few lines of code, this complex request can be executed by using indexed searches:
CREATE EMPTY SET([Dealers];"Winners") ` Create an empty set
SCAN INDEX([Dealers]Sales amount;100;<) ` Scan from the end of the index
CREATE SET([Dealers];"100 best Dealers") ` Put the selected records in a set
For($Country;1;Records in table([Countries])) ` For each Country
` Search for the dealers in this country
QUERY([Dealers];[Dealers]Country=[Countries]Name;*) ` ...who sold for more than $50,000
QUERY(&;[Dealers];[Dealers]Sales amount>=50000)
CREATE SET([Dealers];"WinnerDealers") ` Put them in a set
` They should be in the group of 100 best dealers
INTERSECTION("WinnerDealers";"100 best Dealers";"WinnerDealers")
USE SET("WinnerDealers") ` Potential winners for the country
` Sort them by the results in descending order
ORDER BY([Dealers];[Dealers]Sales amount;<)
REDUCE SELECTION([Dealers];3) ` Take the 3 best Dealers
CREATE SET([Dealers];"WinnerDealers") ` The winners for the country
` Put them in the worldwide winners list
UNION("WinnerDealers";"TheWinners";"TheWinners")
End for
CLEAR SET("100 best Dealers") ` Don't need this set anymore
CLEAR SET("WinnerDealers") ` Don't need this set anymore
USE SET("The Winners") ` Here you have the Winners
CLEAR SET("The Winners") ` Don't need this set anymore
OUTPUT FORM([Dealers];"Prize letter") ` Select the letter
PRINT SELECTION([Dealers]) ` Print the letters
Product: 4D
Theme: Selection
Number:
351
Created: < 4D v6
4D Language Reference ( 4D v16)
4D Language Reference ( 4D v16.1)
4D Language Reference ( 4D v16.2)
4D Language Reference ( 4D v16.3)
