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RETRIEVE A NO. OF ROWS

RETRIEVE A NO. OF ROWS. ¦ Declare a cursor ¦ Open the cursor ¦ Fetch rows of data ¦ Stop fetching rows ¦ Close the cursor. Declaring (defining) a cursor is done in the data division of your program. DATA DIVISION.

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RETRIEVE A NO. OF ROWS

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  1. RETRIEVE A NO. OF ROWS ¦ Declare a cursor ¦ Open the cursor ¦ Fetch rows of data ¦ Stop fetching rows ¦ Close the cursor

  2. Declaring (defining) a cursor is done in the data division of your program. DATA DIVISION. WORKING-STORAGE SECTION. * * * * * * * * * * * * * * * * * * INCLUDE DECLEGENED STRUCTURES * * * * * * * * * * * * * * * * * * EXEC SQL INCLUDE SQLCA END-EXEC. **** SQL CURSOR DECLARATIONS **** EXEC SQL DECLARE CR1 CURSOR FOR SELECT PROJNO,PROJNAME, DEPTNO,LEADER FROM PROJECT WHERE DEPTNO = :DEPT-NO END-EXEC. This statement declares a cursor which will select the rows from the PROJECT table which have a department number equal to the host variable :DEPT-NO.

  3. Open the cursor Opening the cursor is part of the PROCEDURE DIVISION of a program. This actually causes the SELECT which was coded in the cursor declaration to be executed.

  4. DATA DIVISION. **** SQL CURSOR DECLARATIONS **** EXEC SQL DECLARE CR1 CURSOR FOR SELECT PROJNO,PROJNAME, DEPTNO,LEADER FROM PROJECT WHERE DEPTNO = :DEPT-NO END-EXEC. PROCEDURE DIVISION. PERFORM SCREEN-RETRIEVE. EXEC SQL OPEN CR1 END-EXEC. When the OPEN statement is encountered , the SELECT in the cursor declaration is executed.

  5. The OPEN cursor statement not only executes the SELECTion of data from the DB2 data base, but.... ... it also establishes the initial position of the cursor in the results table. The cursor is placed ready to fetch the first row of data.

  6. Fetch rows of data Once the cursor is open, you can fetch the rows of the results table into program variables for calculations or to be printed. The cursor name is the same as the name of the cursor defined in the DECLARE CURSOR statement.

  7. DATA DIVISION. : : · : . EXEC SQL DECLARE CR1 CURSOR FOR SELECT SALARY FROM EMPLOYEE WHERE DEPTNO = :DEPT-NO END-EXEC. : : · : . PROCEDURE DIVISION. PERFORM SCREEN-RETRIEVE. EXEC SQL OPEN CR1 END-EXEC. EXEC SQL FETCH CR1 INTO :EMP-SAL END-EXEC. IF SQLCODE NOT = 0 PERFORM END-FETCH ELSE PERFORM SUM-AND-FETCH UNTIL SQLCODE NOT = 0. SUM-AND-FETCH. ADD EMP-SAL TO TOTAL-SAL. EXEC SQL FETCH CR1 INTO :EMP-SAL END-EXEC.

  8. Rem: The host variable should have matching data types to the columns returned. If there is more than one column being retrieved, the host variables are listed in the same order as the corresponding fields listed in the cursor declaration. The list of host variables are separated by commas and preceded by colons.

  9. This declaration was used to define a cursor. EXEC SQL DECLARE CR1 CURSOR FOR SELECT EMPNO, LNAME, DEPTNO FROM EMPLOYEE WHERE DEPTNO = :DEPT-NO END-EXEC. Which of the following FETCH statements would be correct to use with this declaration? FETCH CR1 INTO :EM-NO, :DP-NAME, :DP-NO, :DP-MGR FETCH CR1 INTO :DP-NAME, :EM-NO, :DP-NO FETCH CR1 INTO :EM-NO, :EM-NAME, :DP-NO FETCH CR1 INTO :DP-NO, :EM-NO, :EM-NAME

  10. FETCH cursor name INTO host-var1, host-var2 ... ¦ Positions a cursor on the next row and assigns values of that row to host variables. ¦ Each time the FETCH statement is executed, the position of the cursor is advanced to the next row of the active set and the columns of that row are placed into host variables. ¦ Will be in some kind of loop where each row is dealt with in turn.

  11. Closing the Cursor ¦ Closing the cursor releases the system resources associated with maintaining the active set. ¦ The active set becomes undefined and the rows become unavailable to your application. ¦ If you forget to close the cursor DB2 will do it for you when the job ends, but it is a good idea to close the cursor when you are done with it. ¦ You can close and reopen a cursor as many times as you like. ¦ The syntax is: EXEC SQL CLOSE cursor name END-EXEC.

  12. DATA DIVISION. : : · : . EXEC SQL DECLARE CR1 CURSOR FOR SELECT SALARY FROM EMPLOYEE WHERE DEPTNO = :DEPT-NO END-EXEC. : : · : . PROCEDURE DIVISION. PERFORM SCREEN-RETRIEVE. EXEC SQL OPEN CR1 END-EXEC. EXEC SQL FETCH CR1 INTO :EMP-SAL END-EXEC. IF SQLCODE NOT = 0 PERFORM END-FETCH ELSE PERFORM SUM-AND-FETCH UNTIL SQLCODE NOT = 0. SUM-AND-FETCH. ADD EMP-SAL TO TOTAL-SAL. EXEC SQL EXEC SQL FETCH CR1CLOSE CR1 INTO :EMP-SAL END-EXEC.END-EXEC

  13. There are several things to watch for when using a cursor: ¦ The number of names in the host list must be equal to the number of columns in the SELECT clause of the DECLARE CURSOR statement. ¦ Check SQLCODE after each FETCH is executed. - +100 means the active set is empty - 0 means the FETCH executed successfully

  14. Let's review the steps we have learned for using a cursor to select multiple rows: ¦ Declare a cursor defines a cursor using a standard SQL SELECT statement. ¦ Open the cursor opens a cursor so that it can be used to fetch rows from its active set. ¦ Fetch rows of data positions a cursor on the next row of its active set and assigns the values of that row to the host variables. ¦ Stop fetching rows by using the value passed in the SQLCODE to determine when all rows from the active set have been fetched. ¦ Close the cursor to destroy the temporary table created when a cursor was opened.

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