version 3
REDUCE SELECTION ({aTable; }number)
Parameter | Type | Description | |
aTable | Table | Table for which to reduce the selection, or | |
Default table, if omitted | |||
number | Number | Number of records to keep selected |
Description
REDUCE SELECTION creates a new selection of records for aTable. The command returns the first number of records from the current selection table. 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(0) is executed, there is no longer any selection nor any current records in the aTable.
Examples
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
See Also
ORDER BY, QUERY, SCAN INDEX, Sets.