DB2

2 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Session Plan SPUFI Hands On Introduction to Embedded SQL DCLGEN Hands On SQLCA Copy Book and its Use Single Row Manipulation Multiple Row Manipulation Cursors

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9 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a SPUFI SQL Processor Using File Input

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19 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a EMBEDDED SQL

20 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Embedded SQL Embedded SQL refers to the use of standard SQL statements within a high-level language program such as COBOL, PL1, C, PASCAL, etc,. The high level language is called Host language Embedded SQL statements are preprocessed by SQL Pre processor before the application program is compiled

21 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Embedded SQL Embedded SQL syntax is almost same as the SQL syntax used in interactive mode. The output of a query is directed to a pre-defined set of variables instead of the terminal. These variables are defined in the host language and are referred to as the host variables. An additional INTO clause is placed after the SQL SELECT statement.

22 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Types of SQL 1.Static SQL: The application programmer knows in advance the SQL statement completely. 2. Dynamic SQL: The application programmer is unaware of the SQL statement in advance. This requires dynamic compilation and binding.

23 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Host Variables(1 of 2) Host variables are just like any other variable of the high level language They are referred as host variables because they are used for receiving data from the table or inserting data to the table. One must declare host variables for all values that are to be passed between the application program and DB2. The host variables may appear anywhere in the WORKING-STORAGE SECTION. The data types of the DB2 columns and corresponding host variables must be compatible.

24 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Host variables (2 of 2) The host variables can not be group items, the only exception to this rule is the variable corresponding to VARCHAR. The host variables may be grouped together in a host structure. The host variables can be Redefined The host variable cannot be Renamed.

25 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Declaring Host Variables Need to declare in the working-storage section of your program EXEC SQL BEGIN DECLARE SECTION END-EXEC. 01 EMPLOYEE-REC. 03 EMP-NO PIC S9(4) COMP. 03 EMP-NAME PIC X(15). 03 EMP-ADDRESS. 49 EMP-ADDRESS-LEN PIC S9(4) COMP. 49 EMP-ADDRESS-TEXT PIC X(25). EXEC SQL END DECLARE SECTION END-EXEC.

26 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a DCLGEN Generating copybook of host variables

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38 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Using DCLGEN copybook EXEC SQL INCLUDE STUD627 END-EXEC

39 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a SQLCA This is the communication area (a copybook containing some variables) through which DB2 passes the feedback of SQL execution to the program In the working-storage section use WORKING-STORAGE SECTION. EXEC SQL INCLUDE SQLCA END-EXEC.

40 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a SQLCA Copy Book (1 Of 3) 01 SQLCA. 03 SQLCAID PIC X(8). 03 SQLCABC PIC S9(9) COMP. 03 SQLCODE PIC S9(9) COMP VALUE SQLERRM. 49 SQLERRML PIC S9(4) COMP. 49 SQLERRMC PIC X(70). 03 SQLERRP PIC X(8). 03 SQLERRD OCCURS 6 PIC S9(9) COMP. 03 SQLWARN. 05 SQLWARN0 PIC X. 05 SQLWARN1 PIC X. 05 SQLWARN2 PIC X. 05 SQLWARN3 PIC X. 05 SQLWARN4 PIC X. 05 SQLWARN5 PIC X. 05 SQLWARN6 PIC X. 05 SQLWARN7 PIC X. 03 SQLSTATE PIC X(5 )

41 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a 03 SQLCAID For Reading dumps. 03 SQLCABC Length of SQLCA (136 bytes). 03 SQLCODE = 0 (Successful) = +ve (Exceptional condition) = -ve(Failure) 03 SQLERRM. 49 SQLERRML Error Message Length. 49 SQLERRMC Error Message Text. 03 SQLERRP Info about internal Error. 03 SQLERRD(1)Internal Error Code. 03 SQLERRD(2)Internal Error Code. 03 SQLERRD(3)Number of Rows affected by INSERT, UPDATE and DELETE. 03 SQLERRD(4)Estimate of resources needed by dynamic SQL statement. 03 SQLERRD(5)Info about dynamic SQL. 03 SQLERRD(6)Internal Error Code. SQLCA Copy Book (2 of 3)

42 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a 05 SQLWARN0 ‘W’ if any other SQLWARNx fields are set to ‘W’. 05 SQLWARN1 ‘W’ indicates truncation of character strings. 05 SQLWARN2 ‘W’ indicates null values were ignored. Ex: AVG, COUNT. 05 SQLWARN3 ‘W’ indicates more columns than host variables. 05 SQLWARN4 ‘W’ indicates no WHERE clause for UPDATE or DELETE. 05 SQLWARN5 ‘W’ indicates SQL/DS statement. 05 SQLWARN6 ‘W’ for adjustment of DATE. 05 SQLWARN7Reserved for Future use. SQLCA Copy Book (3 of 3)

43 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Programming guidelines (1 of 2) Every SQL statement must be coded between columns 12 and 72. Every SQL statement must be delimited between EXEC SQL and END-EXEC. All the tables that are used in a program are to be declared in the WORKING- STORAGE SECTION. This can be done using INCLUDE statement All SQL statements other than INCLUDE and DECLARE TABLE must appear in PROCEDURE DIVISION. Anything on a line within an SQL statement following two hyphens is treated as a comment. Even * can be coded in column 7 for comments.

44 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Single Row Manipulation (1 of 6) EXEC SQL SELECT EMPNO, SALARY INTO :WS-EMPNO, :WS-SALARY FROM EMMPLOYEE WHERE NAME = :WS-NAME END-EXEC SELECT IF SQLCODE = 0 CONTINUE ELSE IF SQLCODE = -811 DISPLAY “MULTIPLE ROWS” ELSE PERFORM C9000-ERROR-PARA. Error Handling

45 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Single Row Manipulation (2 of 6) EXEC SQL INSERT INTO EMPLOYEE (EMPNO, NAME, SALARY) VALUES (:WS-EMPNO, :WS-NAME, :WS-SALARY) END-EXEC INSERT IF SQLCODE = 0 CONTINUE ELSE DISPLAY “UNIDENTIFIED ERROR OCCURRED”. Error Handling

46 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Single Row Manipulation (3 of 6) EXEC SQL UPDATE EMPLOYEE SET SALARY = :WS-SALARY WHERE EMPNO = END-EXEC UPDATE IF SQLCODE = 0 CONTINUE ELSE DISPLAY “UNIDENTIFIED ERROR OCCURRED”. Error Handling

47 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Single Row Manipulation (4 of 6) EXEC SQL DELETE FROM EMPLOYEE WHERE EMPNO = :WS-EMPNO END-EXEC DELETE IF SQLCODE = 0 CONTINUE ELSE DISPLAY “UNIDENTIFIED ERROR OCCURRED”. Error Handling

48 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Single Row Manipulation (5 of 6) EXEC SQL SELECT NAME, SALARY INTO :WS-NAME, :WS-SALARY:WS-SALARY-IND FROM EMPLOYEE WHERE EMPNO = :WS-EMPNO END-EXEC Selecting Nullable columns(Columns which can take NULL values) Indicator variable values and their meanings (1) 0Not Null (2)-1Null (3)-2Exceptional condition

49 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Single Row Manipulation (6 of 6) MOVE-1 TO WS-SALARY-IND EXEC SQL INSERT INTO EMPLOYEE(SALARY) VALUES:WS-SALARY:WS-SALARY-IND END-EXEC Inserting Null values to columns IF SQLCODE = 0 CONTINUE ELSE DISPLAY “UNIDENTIFIED ERROR OCCURRED”. Error Handling

50 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Cursors (1 of 7) Are memory structures used to handle multiple row selections at a time. Conceptually they is a results table used by DB2 to contain the multiple results of a query. They are data structures which hold some/all the results of a query. Are defined in the WORKING- STORAGE SECTION/ PROCEDURE DIVISION.

51 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Cursors (2 of 7) Operations associated with a Cursor 1.DECLARE 2.OPEN 3.FETCH 4.CLOSE

52 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a EXEC SQL DECLARE EMPCUR CURSOR FOR SELECT EMPNO,NAME,SALARY FROM EMPLOYEE WHERE EMPNO > :WS-EMPNO END-EXEC Declaring a Cursor Note: This is just the definition, DB2 executes this statement when we open it. Cursors (3 of 7)

53 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a EXEC SQL OPEN EMPCUR END-EXEC Opening a Cursor Cursors (4 of 7) EXEC SQL CLOSE EMPCUR END-EXEC Closing a Cursor

54 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a EXEC SQL FETCH EMPCUR INTO :WS-EMPNO,:WS-NAME,:WS-SALARY END-EXEC Fetching results from a cursor Cursors (5 of 7) Remarks: 1. We get one row at a time. 2. Only forward READ till SQLCODE = 100.

55 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a EXEC SQL DECLARE EMPCUR CURSOR SELECT EMPNO, NAME, SALARY FROM EMPLOYEE WHERE EMPNO > :WS-EMPNO FOR UPDATE OF SALARY END-EXEC Fetching to Update Cursors (6 of 7) Note: This gives a U lock on the records.

56 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a EXEC SQL UPDATE EMPLOYEE SET SALARY = :WS-SALARY WHERE CURRENT OF EMPCUR END-EXEC Updating a row fetched from a cursor Cursors (7 of 7) Note: This updates exactly one row even if we do not give the key value.

57 Copyright © 2005, Infosys Technologies Ltd ER/CORP/CRS/DB01/003 Version No:2.0a Summary SPUFI Hands On Introduction to Embedded SQL DCLGEN Hands On SQLCA Copy Book and its Use Single Row Manipulation Multiple Row Manipulation Cursors

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