OP Reduce selection

version 1.5

OP Reduce selection (connectionID; tableID; selectionSize) Longint

Parameter	Type		Description
connectionID	Longint		Connection ID with target server
tableID	Longint		Number of the table in the database
selectionSize	Longint		New size for the target table's current selection
Function result	Longint		Error code result for the function

OP Reduce selection creates a new selection of records for table tableID. The new selection contains the first selectionSize records from previous current selection in table tableID.

If selectionSize is greater than the number of records in the current selection, all the records in the selection are selected.

If OP Reduce selection executes successfully, it returns 0. Otherwise, this function returns one of the following errors:

Error Code	Description
-9972	Table number is out of range.
10128	The 4D Open for 4th Dimension package has not been initialized.
10136	The connection does not exist.
10154	This command cannot be executed right now.

This example finds the average amount of the top ten invoices of last year.

   C_LONGINT(vRecords; $ErrCode)
   C_REAL(vValue;vMeanAmount)
   C_LONGINT(vTable;vFieldDate;vFieldAmount)

   $errCode:=OP Get one field number (vConnectID;"[Invoices]Invoice date";vTable;vFieldDate)   
   $errCode:=OP Get one field number (vConnectID;"[Invoices]Invoice amount";vTable;vFieldAmount)
   
      `Compute last year's 1st of January
   vValue:="01/01/" + String ( year of ( Current date ) -1;"####") 
 
      ` Query for last year's invoices
   $errCode:=OP Single query (vConnectID;vTable;vFieldDate;">";->vValue;vRecords)

      `Order by decreasing amount (largest amount is first of selection)
   $errCode:=OP Single order by (vConnectID;vTable;vFieldAmount;"<") 
   
      ` Focus on the 10 largest invoices
   $errCode:=OP Reduce selection (vConnectID;vTable;10)

      `compute mean value
   $errCode:=OP Sum (vConnectID;vTable;vFieldAmount;vMeanAmount)

   ALERT (" Mean value for last year's top ten invoices is :"+ String (vMeanAmount;"### ### ###.##"))

OP All records, OP Records in selection, OP Single order by, OP Single query, REDUCE SELECTION.