PL/SQL User's Guide and Reference
Sample 5. Embedded PL/SQL
The following example shows how you can embed PL/SQL in a high-level host language such as C and demonstrates how a banking debit transaction might be done.
Input Table
SQL> SELECT * FROM accounts ORDER BY account_id;
ACCOUNT_ID BAL
---------- ---------
1 1000
2 2000
3 1500
4 6500
5 500
PL/SQL Block in a C Program
/* available online in file SAMPLE5 */
#include <stdio.h>
char buf[20];
EXEC SQL BEGIN DECLARE SECTION;
int acct;
double debit;
double new_bal;
VARCHAR status[65];
VARCHAR uid[20];
VARCHAR pwd[20];
EXEC SQL END DECLARE SECTION;
EXEC SQL INCLUDE SQLCA;
main()
{
extern double atof();
strcpy (uid.arr,"scott");
uid.len=strlen(uid.arr);
strcpy (pwd.arr,"tiger");
pwd.len=strlen(pwd.arr);
printf("\n\n\tEmbedded PL/SQL Debit Transaction Demo\n\n");
printf("Trying to connect...");
EXEC SQL WHENEVER SQLERROR GOTO errprint;
EXEC SQL CONNECT :uid IDENTIFIED BY :pwd;
printf(" connected.\n");
for (;;) /* Loop infinitely */
{
printf("\n** Debit which account number? (-1 to end) ");
gets(buf);
acct = atoi(buf);
if (acct == -1) /* Need to disconnect from Oracle */
{ /* and exit loop if account is -1 */
EXEC SQL COMMIT RELEASE;
exit(0);
}
printf(" What is the debit amount? ");
gets(buf);
debit = atof(buf);
/* ---------------------------------- */
/* ----- Begin the PL/SQL block ----- */
/* ---------------------------------- */
EXEC SQL EXECUTE
DECLARE
insufficient_funds EXCEPTION;
old_bal NUMBER;
min_bal NUMBER := 500;
BEGIN
SELECT bal INTO old_bal FROM accounts
WHERE account_id = :acct;
-- If the account doesn't exist, the NO_DATA_FOUND
-- exception will be automatically raised.
:new_bal := old_bal - :debit;
IF :new_bal >= min_bal THEN
UPDATE accounts SET bal = :new_bal
WHERE account_id = :acct;
INSERT INTO journal
VALUES (:acct, 'Debit', :debit, SYSDATE);
:status := 'Transaction completed.';
ELSE
RAISE insufficient_funds;
END IF;
COMMIT;
EXCEPTION
WHEN NO_DATA_FOUND THEN
:status := 'Account not found.';
:new_bal := -1;
WHEN insufficient_funds THEN
:status := 'Insufficient funds.';
:new_bal := old_bal;
WHEN OTHERS THEN
ROLLBACK;
:status := 'Error: ' || SQLERRM(SQLCODE);
:new_bal := -1;
END;
END-EXEC;
/* -------------------------------- */
/* ----- End the PL/SQL block ----- */
/* -------------------------------- */
status.arr[status.len] = '\0'; /* null-terminate */
/* the string */
printf("\n\n Status: %s\n", status.arr);
if (new_bal >= 0)
printf(" Balance is now: $%.2f\n", new_bal);
} /* End of loop */
errprint:
EXEC SQL WHENEVER SQLERROR CONTINUE;
printf("\n\n>>>>> Error during execution:\n");
printf("%s\n",sqlca.sqlerrm.sqlerrmc);
EXEC SQL ROLLBACK RELEASE;
exit(1);
}
Interactive Session
Embedded PL/SQL Debit Transaction Demo
Trying to connect... connected.
** Debit which account number? (-1 to end) 1
What is the debit amount? 300
Status: Transaction completed.
Balance is now: $700.00
** Debit which account number? (-1 to end) 1
What is the debit amount? 900
Status: Insufficient funds.
Balance is now: $700.00
** Debit which account number? (-1 to end) 2
What is the debit amount? 500
Status: Transaction completed.
Balance is now: $1500.00
** Debit which account number? (-1 to end) 2
What is the debit amount? 100
Status: Transaction completed.
Balance is now: $1400.00
** Debit which account number? (-1 to end) 99
What is the debit amount? 100
Status: Account not found.
** Debit which account number? (-1 to end) -1
Output Tables
SQL> SELECT * FROM accounts ORDER BY account_id;
ACCOUNT_ID BAL
---------- -----
1 700
2 1400
3 1500
4 6500
5 500
SQL> SELECT * FROM journal ORDER BY date_tag;
ACCOUNT_ID ACTION AMOUNT DATE_TAG
---------- -------------------------- ---------- ---------
1 Debit 300 28-NOV-88
2 Debit 500 28-NOV-88
2 Debit 100 28-NOV-88