Q(uick)BASIC Keyword: ALL

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ALL Keyword

ROLLBACK, ROLLBACK ALL Statements

Worth knowing

Useful and cross-version information about the programming environments of QBasic and QuickBasic.

Syntax

ROLLBACK [savepoint%]
ROLLBACK ALL

Description/Parameter(s)

savepoint%

The savepoint to which a transaction should be rolled back.

Example

This example uses the DELETE statement to remove records from an ISAM file. It creates a transaction with the BEGINTRANS and COMMITTRANS statements, and uses the SAVEPOINT function and ROLLBACK statement within the transaction to provide rollback of any or all of the deletions.Note: To run this program, you must load the ISAM TSR program ROLLBACK. Also, this program assumes a file called BOOKS.MDB exists in the current directory. BOOKS.MDB is a sample ISAM file that SETUP copies to your disk.

DEFINT A-Z
TYPE Borrower
    Cardnum AS LONG             'Card number.
    TheName AS STRING * 36      'Name.
    Street AS STRING * 50       'Street.
    City AS STRING * 26         'City.
    State AS STRING * 2         'State.
    Zip AS LONG                 'Zip code.
END TYPE
 
DIM People AS Borrower          'Record structure variable.
CONST Database = "BOOKS.MDB"    'Name of the disk file.
CONST Tablename = "Cardholders" 'Name of the table.
CONST viewbottom = 17, viewtop = 3, msgtxt = " *** Deleted: Savepoint "
DIM SavePts(viewbottom - viewtop + 1)
 
    TableNum = FREEFILE
    OPEN Database FOR ISAM Borrower Tablename AS TableNum
 
    'Loop until user chooses to quit.
    DO
  VIEW PRINT
  CLS : COLOR 15, 0
  PRINT SPC(34); "Card Holders"
  PRINT "Card#"; SPC(2); "Name"; SPC(13); "Street";
  PRINT SPC(20); "City"; SPC(6); "State"; SPC(2); "Zip"
  LOCATE 24, 1: PRINT "Choose a key:    ";
  PRINT "D - Delete this record    N - Next record    Q - Quit";
  MOVEFIRST TableNum
  VIEW PRINT viewtop TO viewbottom: COLOR 7, 0: CLS
  vPos = viewtop
 
  'Loop through a screenful of records.
  DO
      'For each record, display and ask user what to do with it.
      RETRIEVE TableNum, People
      LOCATE vPos, 1
      PRINT USING ("#####"); People.Cardnum;
      PRINT "  "; LEFT$(People.TheName, 15); "  ";
      PRINT LEFT$(People.Street, 25); "  ";
      PRINT LEFT$(People.City, 10); "  "; People.State; "   ";
      PRINT USING ("#####"); People.Zip
 
      'Get keystroke from user.
      validkeys$ = "DNQ"
      DO
    keychoice$ = UCASE$(INKEY$)
      LOOP WHILE INSTR(validkeys$, keychoice$) = 0 OR keychoice$ = ""
 
      'Process keystroke.
      SELECT CASE keychoice$
      CASE "D"
    IF NOT inTransaction THEN
        inTransaction = -1
        BEGINTRANS
    END IF
    NumSavePts = NumSavePts + 1
    SavePts(NumSavePts) = SAVEPOINT
    DELETE TableNum
    LOCATE vPos, 7: PRINT msgtxt; NumSavePts; SPC(79 - POS(0));
      CASE "Q"
    EXIT DO
      CASE "N"
    MOVENEXT TableNum
      END SELECT
      vPos = vPos + 1
  LOOP UNTIL EOF(TableNum) OR vPos = viewbottom
 
  'If user didn't delete any records, simply quit.
  IF NumSavePts = 0 THEN EXIT DO
 
  'Allow user to commit deletions, or roll back some or all of them.
  VIEW PRINT: LOCATE 24, 1: PRINT "Choose a key:    ";
  PRINT "R - Rollback to a savepoint   A - Rollback all deletions"
  PRINT SPC(17); "Q - commit deletions and Quit";
  validkeys$ = "RAQ"
  DO
      keychoice$ = UCASE$(INKEY$)
  LOOP WHILE INSTR(validkeys$, keychoice$) = 0 OR keychoice$ = ""
  SELECT CASE keychoice$
  CASE "R"
      VIEW PRINT 24 TO 25: PRINT : PRINT
      DO
    PRINT "Roll back to which savepoint ( 1 -"; NumSavePts; ")";
    INPUT RollbackPt
      LOOP UNTIL RollbackPt > 0 AND RollbackPt <= NumSavePts
      ROLLBACK SavePts(RollbackPt)
      NumSavePts = RollbackPt - 1
  CASE "A"
      NumSavePts = 0
      ROLLBACK ALL
  CASE "Q"
      EXIT DO
  END SELECT
    LOOP
 
    IF inTransaction THEN COMMITTRANS
    CLOSE
    END