db2

2Copyright © 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



SPUFI

SQL Processor Using File Input



EMBEDDEDSQL



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



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.



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.



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.



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.



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.



DCLGEN

Generating copybook of host variables



Using DCLGEN copybook

EXEC SQL INCLUDE STUD627END-EXEC



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.



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 0. 03 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)



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)



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 SQLWARN7 Reserved for Future use.

SQLCA Copy Book (3 of 3)



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.



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 CONTINUEELSE IF SQLCODE = -811 DISPLAY “MULTIPLE ROWS”ELSE PERFORM C9000-ERROR-PARA.

Error Handling




EXEC SQL INSERT INTO EMPLOYEE (EMPNO, NAME, SALARY) VALUES (:WS-EMPNO, :WS-NAME, :WS-SALARY)END-EXEC

INSERT

IF SQLCODE = 0 CONTINUEELSE DISPLAY “UNIDENTIFIED ERROR OCCURRED”.

Error Handling




EXEC SQL UPDATE EMPLOYEE SET SALARY = :WS-SALARY WHERE EMPNO = 10878END-EXEC

UPDATE


Error Handling




EXEC SQL DELETE FROM EMPLOYEE WHERE EMPNO = :WS-EMPNOEND-EXEC

DELETE


Error Handling




EXEC SQL SELECT NAME, SALARY INTO :WS-NAME, :WS-SALARY:WS-SALARY-IND FROM EMPLOYEE WHERE EMPNO = :WS-EMPNOEND-EXEC

Selecting Nullable columns(Columns which can take NULL values)

Indicator variable values and their meanings

(1) 0 Not Null

(2) -1 Null

(3) -2 Exceptional condition




MOVE -1 TO WS-SALARY-INDEXEC SQL INSERT INTO EMPLOYEE(SALARY) VALUES:WS-SALARY:WS-SALARY-INDEND-EXEC

Inserting Null values to columns


Error Handling



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.



Cursors (2 of 7)Operations associated with a Cursor

1. DECLARE

2. OPEN

3. FETCH

4. CLOSE



EXEC SQL DECLARE EMPCUR CURSOR FOR

SELECT EMPNO,NAME,SALARY FROM EMPLOYEEWHERE 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)



EXEC SQL OPEN EMPCUREND-EXEC

Opening a Cursor

Cursors (4 of 7)

EXEC SQLCLOSE EMPCUR

END-EXEC

Closing a Cursor



EXEC SQL FETCH EMPCUR INTO :WS-EMPNO,:WS-NAME,:WS-SALARYEND-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.



EXEC SQLDECLARE EMPCUR CURSOR SELECT EMPNO, NAME, SALARY FROM EMPLOYEE WHERE EMPNO > :WS-EMPNO FOR UPDATE OF SALARYEND-EXEC

Fetching to Update

Cursors (6 of 7)

Note: This gives a U lock on the records.



EXEC SQLUPDATE EMPLOYEESET SALARY = :WS-SALARYWHERE 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.



Summary

• SPUFI Hands On

• Introduction to Embedded SQL

• DCLGEN Hands On

• SQLCA Copy Book and its Use

• Single Row Manipulation

• Multiple Row Manipulation

• Cursors



Thank You!

db2

Documents

dynamic sql

sql pre processor

atypes of sqlstatic

use of standard sql

application programmer

predefined set of variables

highlevel language program

high level languagethey