QMSelect()

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The QMSelect function generates a select list containing the ids of all records in a file. It is analogous to use of the QMBasic SELECT statement.

 

The function arguments are:

 

FileNois the file number returned by a previous QMOpen() call.

 

ListNois the select list number (0 to 10).

 

 

The QMSelect() function constructs a list of record ids which can subsequently be processed using the QMReadNext() function. Select list 0, the default select list, is used automatically by many QM components to control their action and should, therefore, be used with caution. An unwanted or partially processed select list can be cleared using the QMClearSelect() function.

 

See Select lists in QMClient sessions for a description of the alternative ways to handle select list with QMClient.

The QMSelect() function does not provide any method to select only those records that meet specific conditions or to sort the list. These features can be accessed by executing query processor commands using the QMExecute() function.

 

The example program fragments below build select list 1 and use it to process records from the file open as fClients.

 

 

hmtoggle_plus1C

void QMSelect(int FileNo, int ListNo)

QMSelect(fClients, 1);

while((Id = QMReadNext(1)) != NULL)

{

 Rec = QMRead(fClients, Id, Err);

 if (Err == 0)

  {

   ...process record...

   QMFree(Rec);

  }

 QMFree(Id);

}

 

Note the use of QMFree() to release the dynamically allocated memory from some of the functions in this example.

 

hmtoggle_plus1VB.Net

QMSelect(ByVal FileNo as Integer, ByVal ListNo as Integer)

QMSelect fClients, 1

Do

  Id = QMReadNext(1, Err)

  If Err <> 0 Then Exit Do

  Rec = QMRead(fClients, Id, Err)

  If Err = 0 Then

     ...process record...

  End If

Loop

 

hmtoggle_plus1QMBasic Class Module

Select(FileNo, ListNo)

session->Select(fClients, 1)

loop

  Id = session->ReadNext(1)

until Id = ""

  Rec = session->Read(fClients, Id, Err)

  if Err = 0 then

     ...process record...

  end

repeat

 

hmtoggle_plus1Java

Select(int FileNo, int ListNo)

qm.Select(fClients, 1);

while((Id = qm.ReadNext(1)) != NULL)

{

 Rec = qm.Read(fClients, Id);

 if (qm.ServerError == SV$OK)

  {

   ...process record...

  }

}

 

hmtoggle_plus1Python

Select(FileNo, ListNo)

qm.Select(fClients, 1)

while True:

  Id = qm.ReadNext(1)

  if Id = "": break

  Rec, Err = qm.Read(fClients, Id)

  ...process record...