REDUCE SELECTION

version 3

REDUCE SELECTION ({table; }number)

REDUCE SELECTION creates a new selection of records for table. The command returns the first number of records from the current selection table. REDUCE SELECTION is applied to the current selection of table in the current process. It changes the current selection of table 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 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 $50000
      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

ORDER BY, QUERY, SCAN INDEX, Sets.