1. Chapter 8 Embedded SQL

2. Objectives Embed SQL commands in COBOL statements
Retrieve single rows using embedded SQL
Update a table using embedded INSERT, UPDATE, and DELETE commands
Use cursors to retrieve multiple rows in embedded SQL
Update a database using cursors
Learn how to handle errors in programs containing embedded SQL commands

3. Introduction
Use a procedural language to use embedded SQL commands to accomplish tasks beyond the capabilities of SQL
Use EXEC SQL and END-SQL in COBOL programming to distinguish embedded SQL commands from standard COBOL statements

4. Introduction
DATA DIVISION (WORKING-STORAGE SECTION) contains statements declaring the tables that will be used in processing the database
Communications area includes items that allow SQL to communicate various aspects of processing to the program

5. Introduction
SQLCODE contains a code indicating the fate of the executed statement
Normal = zero
Not normal = value in SQLCODE that indicates problem
PROCEDURE DIVISION contain new statements that will be SQL statements with slight variations

6. DATA DIVISION Tables to be processed are declared in WORKING-STORAGE
Use the DECLARE TABLE command

7. Create SALES_REP Table
EXEC SQL
DECLARE SALES_REP TABLE
(SLSREP_NUMBER DECIMAL (2),
LAST CHAR (10),
FIRST CHAR (8),
STREET CHAR (15),
CITY CHAR (15),
STATE CHAR (2),
ZIP_CODE CHAR (5),
TOTAL_COMMISSION DECIMAL (7,2),
COMMISSION_RATE DECIMAL (3,2) )
END-EXEC.

8. Code for Using Library
EXEC SQL
INCLUDE DECSALES_REP
END-EXEC.

9. COBOL Variables 01 W-SALES-REP. 03 W-SLSREP_NUMBER PIC S9(2) COMP-3.
03 W-LAST PIC X(10).
03 W-FIRST PIC X(8).
03 W-STREET PIC X(15).
03 W-CITY PIC X(15).
03 W-STATE PIC X(2).
03 W-ZIP-CODE PIC X(5).
03 W-TOTAL-COMMISSION PIC S9(5)V9(2) COMP-3.
03 W-COMMISSION-RATE PIC S9V9(2) COMP-3.

10. SQLCA SQL communication area provides feedback to the program Example:
EXEC SQL
INCLUDE SQLCA
END-EXEC.

11. PROCEDURE DIVISION Use Host variables
Proceed the variable with a colon
Replace results of SQL queries in host variables in the INTO CLAUSE
SELECT LAST
INTO :W-LAST
FROM SALES_REP
WHERE SLSREP_NUMBER = “03”
Make provisions for exceptional conditions

12. Example 1
Obtain the last name of sales rep number 03 and place it in W-LAST

13. Retrieve a Single Row and Column
In SQL:
SELECT LAST
FROM SALES_REP
WHERE SLSREP_NUMBER = “03”;
In COBOL:
EXEC SQL
INTO :W-LAST
WHERE SLSREP_NUMBER = “03”
END-EXEC.

14. Example 2
Obtain all information about the sales rep whose number is stored in the host variable W-SLSREP-NUMBER

15. Retrieve a Single Row and All Columns
EXEC SQL
SELECT LAST, FIRST, STREET, CITY, STATE, ZIP_CODE, TOTAL_COMMISSION, COMMISSION RATE
INTO :W-LAST, :W-FIRST, :W-STREEET, :W-CITY,
:W-STATE, :W-ZIP-CODE, :W-TOTAL-COMMISSION,
:W-COMMISSION-RATE
FROM SALES_REP
WHERE SLSREP_NUMBER = :W-SLSREP-NUMBER
END-EXEC.

16. Program to Display Sales Rep Information

17. Program to Display Sales Rep Information (version 2)

18. Example 3
Obtain the last name, first name, and address of the customer whose customer number is stored in the host variable, W-CUSTOMER-NUMBER, as well as the number, last name, and first name of the sales rep who represents this customer

19. Retrieve a Single Row from a Join
EXEC SQL
SELECT CUSTOMER.LAST, CUSTOMER.FIRST, CUSTOMER.STREET, CUSTOMER.CITY, CUSTOMER.STATE, CUSTOMER.ZIP_CODE, CUSTOMER.SLSREP_NUMBER, SALES_REP.LAST, SALES_REP.FIRST
INTO :W-LAST OF :W-CUSTOMER,
:W-FIRST OF :W-CUSTOMER, :W-STREET OF :W-CUSTOMER, :W-CITY OF :W-CUSTOMER,
:W-STATE OF :W-CUSTMOER, :W-ZIP-CODE OF
:W-CUSTOMER, :W-SLSREP-NUMBER OF
:W-CUSTOMER, :W-LAST OF :W-SLAES-REP,
:W-FIRST OF :W-SALES-REP
FROM SALES-REP, CUSTOMER
WHERE SALES-REP.SLSREP_NUMBER = CUSTOMER.SLSREP_NUMBER
AND CUSTOMER.CUSTOMER_NUMBER =
:W-CUSTOMER-NUMBER
END-EXEC.

20. Example 4 Add a row to the SALES_REP table
The sales rep number, last name, first name address, total commission, and credit limit already have been placed in the variables W-SLSREP-NUMBER, W-LAST, W-FIRST, W-STREET, W-CITY, W-STATE, W-ZIP-CODE, W-TOTAL-COMMISION, and W-COMMISSION-RATE, respectively.

21. Insert a Row Into a Table
EXEC SQL
INSERT
INTO SALES_REP
VALUES (:W-SLSREP-NUMBER, :W-LAST, :W-FIRST, :W-STREET, :W-CITY, :W-STATE, :W-ZIP-CODE,
:W-TOTAL-COMMISSION, :W-COMMISSION-RATE)
END-EXEC.

22. Program to Add Sales Reps

23. Example 5
Change the last name of the sales rep whose number currently is stored in W-SLSREP-NUMBER to the value currently stored in W-LAST

24. Change A Single Row In A Table
EXEC SQL
UPDATE SALES_REP
SET LAST = :W-LAST
WHERE SLSREP_NUMBER = :WSLSREP-NUMBER
END-EXEC.

25. Example 6
Add the amount stored in the host variable INCREASE-IN-RATE to the commission rate for all sales reps who currently represent any customer having a credit limit of $1,000

26. Change Multiple Rows in a Table
EXEC SQL
UPDATE SALES_REP
SET COMMISSION_RATE = COMMISSION_RATE + :INCREASE-IN-RATE
WHERE SLSREP_NUMBER IN
(SELECT SLSREP_NUMBER
FROM CUSTOMER
WHERE CREDIT_LIMIT = 1000)
END-EXEC.

27. Example 7
Delete the sales rep whose number currently is stored in W-SLSREP-NUMBER from the SALES_REP table

28. Delete a Single Row From a Table
EXEC SQL
DELETE
FROM SALES_REP
WHERE SLSREP_NUMBER = :W-SLSREP-NUMBER
END-EXEC.

29. Example 8
Delete every order line for the order whose order number currently is stored in the host variable W-ORDER-NUMBER from the ORDER_LINE table

30. DELETE Multiple Rows From a Table
EXEC SQL
DELETE
FROM ORDER_LINE
WHERE ORDER_NUMBER = :W-ORDER-NUMBER
END-EXEC.

31. Multiple-Row SELECT
Example of SELECT statement producing multiple rows
EXEC SQL
SELECT CUSTOMER_NUMBER, LAST, FIRST
INTO :W-CUSTOMER-NUMBER, :W-LAST, :W-FIRST
FROM CUSTOMER
WHERE SLSREP_NUMBER = :W-SLSREP-NUMBER
END-EXEC
Problem:
COBOL can process only one record at a time, where this SQL command produces multiple rows (records)

32. Cursors
Cursor
A pointer to a row in the collection of rows retrieved by a SQL statement
Advances one row at time to provide sequential, record-at-a-time access to the retrieved rows so COBOL can process the rows
Using a cursor, COBOL can process the set of retrieved rows as though they were records in a sequential file.

33. Example 9
Retrieve the number, last name, and first name of every customer represented by the sales rep whose number is stored in the host variable W-SLSREP-NUMBER

34. Using a Cursor EXEC SQL DECLARE CUSTGROUP CUROSR FOR
SELECT CUSTOMER_NUMER, LAST, FIRST
FROM CUSTOMER
WHERE SLSREP_NUMBER = :W-SLSREP-NUMBER
END-EXEC.

35. OPEN, FETCH,CLOSE
OPEN, FETCH, and CLOSE commands are used in processing a cursor
Analogous to the OPEN, READ, and CLOSE commands used in processing a sequential file

36. Opening a Cursor
EXEC SQL
OPEN CUSTGROUP
END-EXEC.

37. Before OPEN

38. After OPEN, But Before First FETCH

39. Fetching Rows from a Cursor
EXEC SQL
FETCH CUSTGROUP
INTO :W-CUSTOMER-NUMBER, :W-LAST, :W-FIRST
END-EXEC.

40. After First FETCH

41. After Second FETCH

42. After Third FETCH

43. After Attempting a Fourth FETCH

44. Closing a Cursor
EXEC SQL
CLOSE CUSTGROUP
END-EXEC.

45. After CLOSE

46. Program to Display Customers of a Given Sales Rep

47. Example 10
For every order that contains an order line for the part whose part number is stored in W-PART-NUMBER, retrieve the order number, order date, last name, and first name of the customer who placed the order, and the number, last name, and first name of the sales rep who represent the customer
Sort the results by customer number

48. More Complex Cursors EXEC SQL DECLARE ORDGROUP CURSOR FOR
SELECT ORDERS.ORDER_NUMBER, ORDERS.ORDER_DATE, CUSTOMER.CUSTOMER_NUMBER, CUSTOMER.LAST, FIRST, SALES_REP.SLSREP_NUMBER, SALES_REP.LAST, FIRST
FROM ORDER_LINE, ORDERS, CUSTOMER, SALES_REP
WHERE ORDER_LINE.PART_NUMBER = :W-PART-NUMBER
AND ORDER_LINE.ORDER_NUMBER = ORDERS.ORDER_NUMBER
AND ORDERS.CUSTOMER_NUMBER = CUSTOMER.CUSTOMER_NUMBER
AND CUSTOMER.SLSREP_NUMBER = SALES_REP.SLSREP_NUMBER
ORDER BY CUSTOMER.CUSTOMER_NUMBER
END-EXEC.

49. Advantages of Cursors
The coding the in the program is greatly simplified
A special component of the database management system called the optimizer determines the best way to access the data
If the database structure changes in such a way that the necessary information is still obtainable using a different query, the only change required in the program is the cursor definition in WORKING-STORAGE (PRODECURE DIVISION code is not affected)

50. Example 11
Add $100 to the credit limit for every customer represented by the sales rep whose number currently is stored in the host variable W-SLSREP-NUMBER, whose balance is not over the credit limit, and whose credit limit is $500 or less
Add $200 to the credit limit of every customer of this sales rep whose balance is not over the credit limit and whose credit limit is more than $500
Write the number, last name, and first name of every customer of this sales rep whose balance is greater than the credit limit

51. Updating Cursors EXEC SQL DECLARE CREDGROUP CURSOR FOR
SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE, CREDIT_LIMIT
FROM CUSTOMER
WHERE SLSREP_NUMBER = :W-SLSREP-NUMBER
FOR UPDATE OF CREDIT-LIMIT
END-EXEC.

52. Code to FETCH a Row EXEC SQL FETCH CREDGROUP
INTO :W-CUSTOMER-NUMBER, :W-LAST, :W-FIRST, :W-BALANCE, :W-CREDIT-LIMIT
END-EXEC
IF SQLCODE = 100
MOVE “NO” TO ARE-THERE-MORE-CUSTOMERS
ELSE
PERFORM CUSTOMER-UPDATE.
CUSTOMER-UPDATE.
IF W-CREDIT-LIMIT > W-BLANCE
DISPLAY W-FIRST, W-LAST
ELSE IF W-CREDIT-LIMIT > 500
UPDATE CUSTOMER
SET CREDIT-LIMIT = CREDIT_LIMIT + 200
WHERE CURRENT OF CREDGROUP
SET CREDIT_LIMIT = CREDIT_LIMIT + 100
END-EXEC.

53. Error Handling Two types of error conditions
Unusual but normal conditions
Abnormal and unexpected conditions or fatal errors.

54. Unusual Conditions Errors
The value in SQLCODE will be a positive number
Appropriate action is to print an error message and continue processing
Appropriate action for END OF DATA (SQLCODE-100) is termination of some loop and continuation with the rest of the program
No error message is required

55. Abnormal and Unexpected Errors
Value in SQLCODE is a negative number
Appropriate action is to print a final message that indicates the problem and terminate the program
Use the WHENEVER statement to handle these errors in a global way

56. WHENEVER Statement EXEC SQL
WHENEVER SQLERROR GOTO ERROR-PROCESSING-ROUTINE
END-EXEC.
WHENEVER SQLWARNING CONTINUE
WHENEVER NOT FOUND CONTINUE

57. Error Codes SQLERROR = abnormal or fatal condition (SQLCODE < 0)
SQLWARNING = unusual but normal conditions (SQLCODE > 0)
NOT FOUND = special warning END OF DATA (SQLCODE =100)

58. Summary
To embed SQL commands in a COBOL program, precede the SQL command with EXEC SQL, and follow the command with END-EXEC
Statements to define the tables to be accessed must appear in the DATA DIVISION
The DATA DIVISION must contain the INCLUDE SQLCA statement, which allows access to the SQL communication area
You can use host language variables (variables that are not columns within a table) in embedded SQL commands by preceding the variable name with a colon

59. Summary
You can use SELECT statements as embedded SQL commands in COBOL programs only when a single row is retrieved
To place the results of a SELECT statement into host language variables, use the INTO clause in the SELECT command
You can use INSERT, UPDATE, and DELETE statements in COBOL programs, even when they affect more than one row
If a SELECT statement is to retrieve more than one row, it must be used to define a cursor that will be used to select one row at a time

60. Summary
To activate a cursor, use the OPEN command to execute the query in the cursor definition
To select the next row in COBOL, use the FETCH command
To deactivate a cursor, use the CLOSE command. The rows initially retrieved will not longer be available to COBOL
DATA in the tables on which a cursor is based can be updated by including the WHERE CURRENT OF cursor name clause in the update statement
This clause updates only the current (most recently fetched) row

61. Summary To see if an error has occurred, examine the value in SQLCODE
Rather than checking SQLCODE in every place in the program where errors could occur, use the WHENEVER clause