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ALLBASE/SQL FORTRAN Application Programming Guide: HP 9000 Computer Systems > Chapter 8 Processing with Cursors![]() Program Using UPDATE WHERE CURRENT |
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The flow chart in Figure 8-4 summarizes the functionality of program forex8. This program uses a cursor and the UPDATE WHERE CURRENT command to update column ReceivedQty in table PurchDB.OrderItems. The runtime dialog for forex8 appears in Figure 8-5, and the source code in Figure 8-6. The main program 1 first executes subroutine DeclareCursor 9, which contains the DECLARE CURSOR command. This command is a preprocessor directive and is not executed at runtime. At runtime, subroutine DeclareCursor only displays the message Declare Cursor. The DECLARE CURSOR command defines a cursor named OrderReview. The cursor is associated with a SELECT command that retrieves the following columns for all rows in table PurchDB.OrderItems having a specific order number but no null values in column VendPartNumber: OrderNumber (defined NOT NULL) ItemNumber (defined NOT NULL) VendPartNumber ReceivedQty Cursor OrderReview has a FOR UPDATE clause naming column ReceivedQty to allow the user to change the value in this column. Next, to establish a DBE session, program forex8 executes function ConnectDBE 3. This function evaluates to TRUE when the CONNECT command for the sample DBEnvironment, PartsDBE, is successfully executed. The program then executes function FetchUpdate 13 until the Done flag is set to TRUE. Function FetchUpdate 13 prompts for an order number or a 0. When the user enters a 0, FetchUpdate is set to FALSE, which in turn sets the Done flag to FALSE, and the program terminates. When the user enters an order number, the program begins a transaction by executing subroutine BeginTransaction 6, which executes the BEGIN WORK command. Cursor OrderReview is then opened by invoking function OpenCursor 10. This function, which executes the OPEN CURSOR command, evaluates to TRUE when the command is successful. A row at a time is retrieved and optionally updated until the Fetch flag is set to FALSE. This flag becomes false when:
The FETCH command 13B names an indicator variable for ReceivedQty, the only column in the query result that may contain a null value. If the FETCH command is successful, the program executes subroutine DisplayUpdate 12 to display the current row and optionally update it. Subroutine DisplayUpdate 12 executes subroutine DisplayRow 8 to display the current row. If column ReceivedQty in the current row contains a null value, the message, ReceivedQty is NULL, is displayed. The user is then asked whether he wants to update the current ReceivedQty value 12A. If so, the user is prompted for a new entry. Depending on the user's response, the program assigns an appropriate value to the indicator variable ReceivedQtyInd, and then issues the UPDATE WHERE CURRENT command 12B. If the user enters a 0, the indicator variable is set to -1 and a null value is assigned to this column. If the user enters a non-zero value, the indicator variable is set to 0 and the user-entered value is assigned to the column. The program then asks whether to FETCH another row. If so, the FETCH command is re-executed. If not, the program asks whether the user wants to make permanent any updates he may have made in the active set. To keep any row changes, the program executes subroutine CommitWork 6, which executes the COMMIT WORK command. To undo any row changes, the program executes subroutine RollBackWork 7, which executes the ROLLBACK WORK command. The COMMIT WORK command is also executed when ALLBASE/SQL sets SQLCode to 100 following execution of the FETCH command. SQLCode is set to 100 when no rows qualify for the active set or when the last row has already been fetched. If the FETCH command fails for some other reason, the ROLLBACK WORK command is executed instead. Before any COMMIT WORK or ROLLBACK WORK command is executed, cursor OrderReview is closed. Although the cursor is automatically closed whenever a transaction is terminated, it is good programming practice to use the CLOSE command to close open cursors prior to terminating transactions. When the program user enters a 0 in response to the order number prompt 13A, the program terminates by executing subroutine TerminateProgram 4, which executes the RELEASE command 2. Explicit status checking is used throughout this program. After each embedded SQL command is executed, SQLCA.SQLCode is checked. If SQLCode is less than 0, the program executes subroutine SQLStatusCheck 2, which executes the SQLEXPLAIN command. Figure 8-4 Flow Chart of Program forex8 ![]() Figure 8-5 Runtime Dialog of Program forex8 :run forex8 Program to UPDATE OrderItems table via a CURSOR -- forex8 Event List: CONNECT TO ../sampledb/PartsDBE Prompt for Order Number BEGIN WORK OPEN Cursor FETCH a row Display the retrieved row Prompt for new Received Quantity UPDATE row within OrderItems table FETCH the next row, if any, with the same Order Number Repeat the above five steps until no more rows qualify CLOSE Cursor COMMIT WORK or ROLLBACK WORK Repeat the above eleven steps until user enters 0 RELEASE ../sampledb/PartsDBE Declare Cursor OrderReview CONNECT TO ../sampledb/PartsDBE Enter Order Number or a 0 to STOP >30520 BEGIN WORK OPEN the Declared Cursor OrderReview OrderNumber: 30520 ItemNumber: 1 VendPartNumber: 9375 ReceivedQty: 9 Do you want to change ReceivedQty (Y/N)? > n Do you want to see another row (Y/N)? > y OrderNumber: 30520 ItemNumber: 2 VendPartNumber: 9105 ReceivedQty: 3 Do you want to change ReceivedQty (Y/N)? > y Enter New ReceivedQty or a 0 for NULL> 15 Do you want to see another row (Y/N)? > y OrderNumber: 30520 ItemNumber: 3 VendPartNumber: 9135 ReceivedQty: 3 Do you want to change ReceivedQty (Y/N)? > n Do you want to see another row (Y/N)? > y Row not found or no more rows! Do you want to save your changes (Y/N)? > n CLOSE the Declared Cursor OrderReview ROLLBACK WORK No Rows Changed! Enter Order Number or a 0 to STOP > 30510 BEGIN WORK OPEN the Declared Cursor OrderReview OrderNumber: 30510 ItemNumber: 1 VendPartNumber: 1001 ReceivedQty: 3 Do you want to change ReceivedQty (Y/N)? > n Do you want to see another row (Y/N)? > n CLOSE the Declared Cursor OrderReview COMMIT WORK Enter Order Number or a 0 to STOP > 0 User entered a 0 RELEASE ../sampledbPartsDBE $ Figure 8-6 Program forex8: Using UPDATE WHERE CURRENT PROGRAM forex8 C* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * C* This program illustrates the use of UPDATE WHERE CURRENT* C* with a Cursor to update a single row at a time. * C* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * IMPLICIT NONE LOGICAL*2 Done, ConnectDBE, FetchUpdate C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA C (* Beginning of the Main Program *) 1 WRITE (*,*) CHAR(27), 'U' WRITE (*,*) 'Program to UPDATE OrderItems table via a 1CURSOR -- forex8' WRITE (*,*) ' ' WRITE (*,*) 'Event List:' WRITE (*,*) ' CONNECT TO ../sampledb/PartsDBE' WRITE (*,*) ' Prompt for Order Number' WRITE (*,*) ' BEGIN WORK' WRITE (*,*) ' OPEN Cursor' WRITE (*,*) ' FETCH a row' WRITE (*,*) ' Display the retrieved row' WRITE (*,*) ' Prompt for new Received Quantity' WRITE (*,*) ' UPDATE row within OrderItems table' WRITE (*,*) ' FETCH the next row, if any, with the 1same Order Num 1ber' WRITE (*,*) ' Repeat the above five steps until no 1more rows qual 1ify' WRITE (*,*) ' CLOSE Cursor' WRITE (*,*) ' COMMIT WORK or ROLLBACK WORK' WRITE (*,*) ' Repeat the above eleven steps until 1user enters 0' WRITE (*,*) ' RELEASE ../sampledb/PartsDBE' CALL DeclareCursor WRITE (*,*) ' ' IF (ConnectDBE()) THEN Done = .TRUE. DO WHILE (Done) Done = FetchUpdate() END DO CALL TerminateProgram ELSE WRITE (*,*) 'Cannot Connect to your DBEnvironment!' ENDIF STOP END C (* End of Main Program *) C (* Beginning of the Sub-Routines *) SUBROUTINE SQLStatusCheck 2 C**** SUBROUTINE SQLStatusCheck checks status of SQL commands C**** and print HPSQL error messages. C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA LOGICAL*2 Abort, Check INTEGER DeadLock PARAMETER (DeadLock = -14024) C (* Begin Host Variable Declarations *) EXEC SQL BEGIN DECLARE SECTION CHARACTER*120 SQLMessage EXEC SQL END DECLARE SECTION C (* End Host Variable Declarations *) Abort = .FALSE. IF (SQLCode .LT. DeadLock) THEN Abort = .TRUE. WRITE (*,*) 'A serious error has occurred.' ENDIF Check = .TRUE. DO WHILE (Check) EXEC SQL SQLEXPLAIN :SQLMessage WRITE(*, 100) SQLMessage 100 FORMAT(A120) IF (SQLCode .EQ. 0) THEN Check = .FALSE. ENDIF END DO IF (Abort) THEN CALL TerminateProgram STOP 'Program Aborted' END IF RETURN END C (* End of Subroutine SQLStatusCheck *) LOGICAL*2 FUNCTION ConnectDBE() 3 C**** FUNCTION to connect to ../sampledb/PartsDBE INTEGER*2 OK PARAMETER (OK = 0) C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA EXEC SQL BEGIN DECLARE SECTION EXEC SQL END DECLARE SECTION WRITE (*, *) 'CONNECT TO ../sampledb/PartsDBE' EXEC SQL CONNECT TO 'PartsDBE' ConnectDBE = .TRUE. IF (SQLCode .NE. OK) THEN ConnectDBE = .FALSE. CALL SQLStatusCheck ENDIF RETURN END C (* End of Function ConnectDBE *) SUBROUTINE TerminateProgram 4 C**** SUBROUTINE to release from ../sampledb/PartsDBE C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA EXEC SQL BEGIN DECLARE SECTION EXEC SQL END DECLARE SECTION WRITE(*,*) ' ' WRITE(*,*) 'RELEASE ../sampledb/PartsDBE' EXEC SQL RELEASE RETURN END C (* End of Subroutine TerminateProgram *) SUBROUTINE BeginTransaction 5 C**** SUBROUTINE to begin work INTEGER*2 OK PARAMETER (OK = 0) C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA EXEC SQL BEGIN DECLARE SECTION EXEC SQL END DECLARE SECTION WRITE (*,*) 'BEGIN WORK' EXEC SQL BEGIN WORK IF (SQLCode .NE. OK) THEN CALL SQLStatusCheck CALL TerminateProgram ENDIF RETURN END C (* End of Subroutine BeginTransaction *) SUBROUTINE CommitWork 6 C**** SUBROUTINE to commit work INTEGER*2 OK PARAMETER (OK = 0) C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA EXEC SQL BEGIN DECLARE SECTION EXEC SQL END DECLARE SECTION WRITE(*,*) 'COMMIT WORK' EXEC SQL COMMIT WORK IF (SQLCode .NE. OK) THEN CALL SQLStatusCheck CALL TerminateProgram ENDIF RETURN END C (* End of Subroutine CommitWork *) SUBROUTINE RollBackWork 7 C**** SUBROUTINE to RollBack Work INTEGER*2 OK PARAMETER (OK = 0) C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA EXEC SQL BEGIN DECLARE SECTION EXEC SQL END DECLARE SECTION WRITE(*,*) 'ROLLBACK WORK' EXEC SQL ROLLBACK WORK IF (SQLCode .NE. OK) THEN CALL SQLStatusCheck CALL TerminateProgram ENDIF RETURN END C (* End of Subroutine RollBackWork *) SUBROUTINE DisplayRow (OrderNumber,ItemNumber,VendPartNumber, 1 ReceivedQty, ReceivedQtyInd) 8 C**** SUBROUTINE to display OrderItems table rows C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA C (* Begin Host Variable Declarations *) EXEC SQL BEGIN DECLARE SECTION INTEGER OrderNumber INTEGER ItemNumber CHARACTER*16 VendPartNumber INTEGER ReceivedQty SQLIND ReceivedQtyInd CHARACTER*120 SQLMessage EXEC SQL END DECLARE SECTION C (* End Host Variable Declarations *) WRITE(*,*) ' ' WRITE(*, '('' OrderNumber: '',I10)') OrderNumber WRITE(*, '('' ItemNumber: '',I10)') ItemNumber WRITE(*, '('' VendPartNumber: '',A16)') VendPartNumber IF (ReceivedQtyInd .LT. 0) THEN WRITE(*,*) ' ReceivedQty is NULL' ELSE WRITE(*, '('' ReceivedQty: '',I5)') ReceivedQty ENDIF WRITE(*,*) ' ' RETURN END C (* End of Subroutine DisplayRow *) SUBROUTINE DeclareCursor 9 C**** SUBROUTINE to declare the Cursor C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA C (* Begin Host Variable Declarations *) EXEC SQL BEGIN DECLARE SECTION INTEGER OrderNumber INTEGER ItemNumber CHARACTER*16 VendPartNumber INTEGER ReceivedQty SQLIND ReceivedQtyInd CHARACTER*120 SQLMessage EXEC SQL END DECLARE SECTION C (* End Host Variable Declarations *) WRITE (*,*) ' ' WRITE (*,*) 'Declare Cursor OrderReview' WRITE (*,*) ' ' EXEC SQL DECLARE OrderReview 1 CURSOR FOR 2 SELECT OrderNumber, 3 ItemNumber, 4 VendPartNumber, 5 ReceivedQty 6 FROM PurchDB.OrderItems 7 WHERE OrderNumber = :OrderNumber 8 AND VendPartNumber IS NOT NULL 9 FOR UPDATE OF ReceivedQty RETURN END C (* End of Subroutine DeclareCursor *) LOGICAL*2 FUNCTION OpenCursor(OrderNumber, ItemNumber,10 1 VendPartNumber, ReceivedQty, ReceivedQtyInd) C**** FUNCTION to open the Cursor INTEGER OK PARAMETER (OK = 0) C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA C (* Begin Host Variable Declarations *) EXEC SQL BEGIN DECLARE SECTION EXEC SQL END DECLARE SECTION C (* End Host Variable Declarations *) OpenCursor = .TRUE. WRITE (*,*) ' ' WRITE (*,*) 'OPEN the Declared Cursor OrderReview' WRITE (*,*) ' ' EXEC SQL OPEN OrderReview IF (SQLCode .NE. OK) THEN OpenCursor = .FALSE. CALL SQLStatusCheck CALL RollBackWork ENDIF RETURN END C**** (End of Function OpenCursor) SUBROUTINE CloseCursor 11 C**** SUBROUTINE to close the Cursor INTEGER OK PARAMETER (OK = 0) C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA C (* Begin Host Variable Declarations *) EXEC SQL BEGIN DECLARE SECTION EXEC SQL END DECLARE SECTION C (* End Host Variable Declarations *) WRITE (*,*) ' ' WRITE (*,*) 'CLOSE the Declared Cursor OrderReview' WRITE (*,*) ' ' EXEC SQL CLOSE OrderReview IF (SQLCode .NE. OK) THEN CALL SQLStatusCheck CALL TerminateProgram ENDIF RETURN END C**** (End of Subroutine CloseCursor) SUBROUTINE DisplayUpdate(OrderNumber, ItemNumber, 12 1 VendPartNumber, ReceivedQty, ReceivedQtyInd, 2 RowCounter,Fetch) C**** SUBROUTINE to Display and Update a row from PurchDB.OrderItems LOGICAL*2 Fetch CHARACTER Response INTEGER NotFound,MultipleRows,OK,RowCounter PARAMETER (NotFound = 100, 1 MultipleRows = -10002, 2 OK = 0) C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA C (* Begin Host Variable Declarations *) EXEC SQL BEGIN DECLARE SECTION INTEGER OrderNumber INTEGER ItemNumber CHARACTER*16 VendPartNumber INTEGER ReceivedQty SQLIND ReceivedQtyInd CHARACTER*120 SQLMessage EXEC SQL END DECLARE SECTION CALL DisplayRow(OrderNumber, ItemNumber, VendPartNumber, 1 ReceivedQty, ReceivedQtyInd) WRITE (*,100) 12A 100 FORMAT (/$, ' Do you want to change ReceivedQty (Y/N)? > ') READ (*, 110) Response 110 FORMAT(A1) IF ((Response .EQ. 'Y') .OR. (Response .EQ. 'y')) THEN WRITE (*,120) 120 FORMAT (/$,'Enter New ReceivedQty or a 0 for NULL > ') READ (*,130) ReceivedQty 130 FORMAT(I5) IF (ReceivedQty .EQ. 0) THEN ReceivedQtyInd = -1 ELSE ReceivedQtyInd = 0 ENDIF EXEC SQL UPDATE PurchDB.OrderItems 12B 1 SET ReceivedQty = :ReceivedQty :ReceivedQtyInd 2 WHERE CURRENT OF OrderReview IF (SQLCode .NE. OK) THEN CALL SQLStatusCheck ELSE RowCounter = RowCounter +1 ENDIF ENDIF WRITE (*,140) 140 FORMAT (/$, 'Do you want to see another row (Y/N)? > ') READ (*, 150) Response 150 FORMAT (A1) IF ((Response .EQ. 'N') .OR. (Response .EQ. 'n')) THEN IF (RowCounter .GT. 0) THEN WRITE (*,160) 160 FORMAT (/$, 'Do you want to save your changes (Y/N)? >') READ (*, 170) Response 170 FORMAT (A1) IF ((Response .EQ. 'N') .OR. (Response .EQ. 'n')) THEN CALL CloseCursor CALL RollBackWork Fetch = .FALSE. WRITE (*,*) 'No Row(s) Changed! ' ELSE CALL CloseCursor CALL CommitWork Fetch = .FALSE. WRITE (*, '('' Row(s) Changed: '',I2)') RowCounter ENDIF ELSEIF (RowCounter .EQ. 0) THEN CALL CloseCursor CALL CommitWork Fetch = .FALSE. ENDIF ENDIF RETURN END C**(End of Subroutine DisplayUpdate) LOGICAL*2 FUNCTION FetchUpdate() 13 C**FUNCTION to Fetch rows from PurchDB.OrderItems table. CHARACTER Response LOGICAL*2 Fetch,OpenCursor INTEGER NotFound,MultipleRows,OK,RowCounter PARAMETER (NotFound = 100, 1 MultipleRows = -10002, 2 OK = 0) C (* Begin SQL Communication Area *) EXEC SQL INCLUDE SQLCA C (* Begin Host Variable Declarations *) EXEC SQL BEGIN DECLARE SECTION INTEGER OrderNumber INTEGER ItemNumber CHARACTER*16 VendPartNumber INTEGER ReceivedQty SQLIND ReceivedQtyInd CHARACTER*120 SQLMessage EXEC SQL END DECLARE SECTION C (* End Host Variable Declarations *) RowCounter = 0 FetchUpdate = .TRUE. WRITE (*,100) 13A 100 FORMAT(/$, 'Enter Order Number or a 0 to stop > ') READ (*,110) OrderNumber 110 FORMAT(I10) IF (OrderNumber .NE. 0) THEN CALL BeginTransaction IF (OpenCursor(OrderNumber,ItemNumber, 1 VendPartNumber,ReceivedQty,ReceivedQtyInd)) THEN Fetch = .TRUE. DO WHILE (Fetch) EXEC SQL FETCH OrderReview 13B 1 INTO :OrderNumber, 1 :ItemNumber, 2 :VendPartNumber, 3 :ReceivedQty :ReceivedQtyInd IF (SQLCode .EQ. OK) THEN CALL DisplayUpdate(OrderNumber,ItemNumber,VendPartNumber, 1 ReceivedQty, ReceivedQtyInd, RowCounter,Fetch) ELSEIF (SQLCode .EQ. NotFound) THEN Fetch = .FALSE. WRITE (*,*) ' ' WRITE (*,*) 'Row not found or no more rows!' IF (RowCounter .GT. 0) THEN WRITE (*,120) 120 FORMAT (/$, 'Do you want to save your changes (Y/N)? > ' ) READ (*,130) Response 130 FORMAT(A1) IF ((Response .EQ. 'N') .OR. (Response .EQ. 'n')) THEN CALL CloseCursor CALL RollBackWork WRITE (*,*) 'No Row(s) Changed! ' ELSE CALL CloseCursor CALL CommitWork WRITE (*, '('' Row(s) Changed: '',I2)') RowCounter ENDIF ELSEIF (RowCounter .EQ. 0) THEN CALL CloseCursor CALL CommitWork ENDIF ELSEIF (SQLCode .EQ. MultipleRows) THEN Fetch = .FALSE. WRITE(*,*) ' ' WRITE (*,*) 'WARNING: More than one row qualifies!' CALL SQLStatusCheck ELSE Fetch = .FALSE. CALL SQLStatusCheck CALL CloseCursor CALL RollBackWork ENDIF END DO ELSE FetchUpdate = .FALSE. WRITE (*,*) 'Failed to Open Cursor' ENDIF ELSE FetchUpdate = .FALSE. WRITE (*,*) 'User entered an 0' ENDIF RETURN END C (* End of Subroutine FetchUpdate *) |