1. Copyright
All material contained herein is owned by Daniel Stober, the author of this presentation. This presentation and the queries, examples, and original sample data may be shared with others for educational purposes only in the following circumstances:
That the person or organization sharing the information is not compensated, or
If shared in a circumstance with compensation, that the author has granted written permission to use this work
Using examples from this presentation, in whole or in part, in another work without proper source attribution constitutes plagiarism.
Use of this work implies acceptance of these terms

2. Six Bugs you can put into Your PLSQL Programs
Dan Stober
Intermountain Healthcare
September 14, 2011

3. Dan Stober Data Architect – Intermountain Healthcare
Attended California State Univ., Fresno
Working in Oracle databases since 2001
Frequent presenter at local and national user group conferences
Oracle Open World twice
Private Instructor for Trutek
Teaching PLSQL
Oracle Certified SQL Expert
Board of Trustees – Utah Oracle Users Group
Edit newsletter
Write SQL Tip column

4. Intermountain Healthcare
23 hospitals in Utah and Idaho
Non-profit integrated health care system
750 Employed physicians
32,000 employees
The largest non-government employer in Utah
One of the largest and most complete clinical data warehouses in the world!

5. Session Norms Questions? I learn something from every session I do!
Interrupt Me!
I learn something from every session I do!
Set the record straight!
Cell phones?
OK!

6. Bugs? These are: How did I learn these? My goal? Not bugs in PLSQL
Errors in the code introduced by programmers who missed some of the nuances in the language
Examples of PLSQL behaving exactly as documented
How did I learn these?
I’ve made every one of these mistakes!
My goal?
Make you aware
So you can avoid them

7. Bug Agenda FOR LOOP variables No_data_found Parameter defaults
Function returned without value
Declaration section exceptions
More FOR LOOP issues
Implicit COMMIT

8. Bug #1
FOR LOOP Variables

9. What will be the result? This variable i is the same as this i
DECLARE
i NUMBER := 10;
BEGIN
dbms_output.put_line ( 'i=' || i ) ;
FOR i IN 1..5 LOOP
END LOOP;
END;
This variable i is the same as this i
But, this i is a different variable
i=10
i=1
i=2
i=3
i=4
i=5
PL/SQL procedure successfully completed.

10. The FOR LOOP handles all of these
Components of a LOOP
Duties / Functions
Declaration
Initialization
Iteration
Exit condition
DECLARE
i NUMBER;
BEGIN
i := 1;
LOOP
dbms_output.put_line ( i ) ;
i := i + 1;
EXIT WHEN i > 5;
END LOOP;
END;
Declaration
Initialization
Iteration
Exit Condition
The FOR LOOP handles all of these
BEGIN
FOR i IN 1..5 LOOP
dbms_output.put_line ( i ) ;
END LOOP;
END;

11. Components of a Cursor Loop
DECLARE
CURSOR emps IS SELECT ename
FROM scott.emp;
rec emps%TYPE;
BEGIN
OPEN emps;
LOOP
FETCH emps INTO rec;
EXIT WHEN emps%NOTFOUND;
dbms_output.put_line ( rec.ename )
END LOOP;
CLOSE emps;
END;
Declaration
Open / Close
Record Fetch
Iteration
Exit Condition
Open / Close

12. Components of a Cursor FOR Loop
Declaration
BEGIN
FOR rec IN ( SELECT ename
FROM scott.emp )
LOOP
dbms_output.put_line ( rec.ename )
END LOOP;
END;
Open / Close
Record Fetch
Iteration
Exit Condition

13. How does this manifest as a bug?
Scope of LOOP variables
DECLARE
CURSOR emps IS SELECT empno, ename
FROM scott.emp;
rec emps%TYPE;
BEGIN
FOR rec IN emps LOOP
INSERT INTO myemps VALUES rec;
END LOOP;
EXCEPTION WHEN OTHERS THEN
dbms_output.put_line ( SQLERRM || '>' || rec.empno );
END;
It creates the temptation to reference the loop variable outside of the loop, with the belief that the variable will retain the value that it held inside of the loop.

14. CURSOR FOR variables The same principle applies in a CURSOR FOR LOOP
DECLARE
CURSOR emps_cur is ( SELECT empno, ename, sal
FROM emp ORDER BY empno);
rec emps_cur%TYPE;
BEGIN
FOR rec IN emps_cur LOOP
process_record ( rec.empno );
END LOOP;
IF rec.sal > 1000 THEN
... etc etc etc
The programmer probably intended to read the value from the last record processed. But this is not the same variable

15. One solution Bug #1: Never declare FOR LOOP variables On solution:
Create a separate variable
With a different name
With scope outside of the loop
DECLARE
CURSOR emps IS SELECT empno, ename
FROM scott.emp;
v_empno NUMBER;
BEGIN
FOR rec IN emps LOOP
v_empno := rec.empno;
INSERT INTO myemps VALUES rec;
END LOOP;
EXCEPTION WHEN OTHERS THEN
dbms_output.put_line ( SQLERRM || '>' || v_empno );
END;
Assign the value from the cursor record to a variable with a scope which exceeds the loop boundary.

16. Bug #2
No_data_found

17. No_data_found
Built-in PLSQL exception designed to be used with implicit cursors
Implicit cursor:
Query structure using SELECT xxx INTO xxx
One and only one record is expected
If more than one record:
Too_many_rows
If no records:
No_data_found
Bug: An aggregate function always returns one row
Unless used with GROUP BY

18. Some handlers are not needed
Group functions always return one row
SQL> SELECT COUNT(*)
2 FROM emp
3 WHERE job = 'DBA';
COUNT(*)
1 row selected.
FUNCTION get_emp_job_count ( p_job IN VARCHAR2 )
RETURN NUMBER IS
v_ret_val NUMBER;
BEGIN
SELECT COUNT(*)
INTO v_ret_val
FROM emp
WHERE job = p_job;
EXCEPTION
WHEN no_data_found THEN
v_ret_val := 0;
END;
RETURN v_ret_val;
So what?
The handler isn’t needed.
It might be extra clutter,
but does that make it a bug?
This exception will never be raised

19. This exception will never be raised
Unused handler
FUNCTION get_job_sal_sum ( p_job IN VARCHAR2 )
RETURN NUMBER IS
v_ret_val NUMBER;
BEGIN
SELECT SUM( sal )
INTO v_ret_val
FROM emp
WHERE job = p_job;
EXCEPTION
WHEN no_data_found THEN
v_ret_val := 0;
END;
RETURN v_ret_val;
The attempt here is to return ZERO when there are no emps with the job
This exception will never be raised
When called for a JOB with no records in the table, the function will return NULL.
Not ZERO.

20. Calling the Buggy Function
BEGIN
dbms_output.put_line ( 'CLERK: ' || get_job_sal_sum ( 'CLERK'));
dbms_output.put_line ( 'DBA: ' || get_job_sal_sum ( 'DBA'));
dbms_output.put_line ( 'SALESMAN: ' || get_job_sal_sum ( 'SALESMAN'));
END; /
CLERK: 4150
DBA:
SALESMAN: 5600
PL/SQL procedure successfully completed.
BEGIN
dbms_output.put_line ( 'CLERK: ' || get_job_sal_sum ( 'CLERK'));
dbms_output.put_line ( 'DBA: ' || get_job_sal_sum ( 'DBA'));
dbms_output.put_line ( 'SALESMAN: ' || get_job_sal_sum ( 'SALESMAN'));
END;
The function returned NULL
The query DID return a record, thus no_data_found was not raised, so the function returned the value from the query. It did not get replaced with ZERO.
Here’s the query that was executed on the second call
SQL> SELECT SUM ( sal )
2 FROM emp
3 WHERE job = 'DBA';
SUM(SAL)
1 row selected.

21. Fixing the Buggy Function
FUNCTION get_job_sal_sum ( p_job IN VARCHAR2)
RETURN NUMBER IS
v_ret_val NUMBER;
BEGIN
SELECT SUM( sal )
INTO v_ret_val
FROM emp
WHERE job = p_job;
RETURN NVL ( v_ret_val, 0);
END;
If the variable contains NULL, it will return ZERO instead
BEGIN
dbms_output.put_line ( 'CLERK: ' || get_job_sal_sum ( 'CLERK'));
dbms_output.put_line ( 'DBA: ' || get_job_sal_sum ( 'DBA'));
dbms_output.put_line ( 'SALESMAN: ' || get_job_sal_sum ( 'SALESMAN'));
END;
BEGIN
dbms_output.put_line ( 'CLERK: ' || get_job_sal_sum ( 'CLERK'));
dbms_output.put_line ( 'DBA: ' || get_job_sal_sum ( 'DBA'));
dbms_output.put_line ( 'SALESMAN: ' || get_job_sal_sum ( 'SALESMAN'));
END; /
CLERK: 4150
DBA: 0
SALESMAN: 5600
PL/SQL procedure successfully completed.
Excellent!

22. Another Way to Fix It
FUNCTION get_emp_job_count ( p_job IN VARCHAR2 )
RETURN NUMBER IS
v_ret_val NUMBER;
BEGIN
SELECT COUNT(*)
INTO v_ret_val
FROM emp
WHERE job = p_job
GROUP BY job;
EXCEPTION
WHEN no_data_found THEN
v_ret_val := 0;
END;
RETURN v_ret_val;
With a GROUP BY, the query will return no records, if there is no match!
SQL> SELECT COUNT(*)
2 FROM emp
3 WHERE job = 'DBA'
4 GROUP BY job;
no rows selected

23. Another issue Do you see it?
PROCEDURE process_sal_increase
( p_empno IN NUMBER ) IS
v_current_sal NUMBER;
BEGIN
SELECT sal
INTO v_current_sal
FROM emp
WHERE empno = p_empno
AND ROWNUM = 1;
v_new_sal := calculate_new_sal ( p_empno, v_sal );
END;
If the WHERE clause returns more than one record, and you don’t care which one you get, then why bother selecting?
- Tom Kyte, paraphrased
Why is this here?
When you see this, it usually means that too_many_rows was raised at some point. Instead of fixing the data or the WHERE clause, the developer added this

24. An Aside: Performance Bug
DECLARE
V_rec_cnt INTEGER;
BEGIN
SELECT COUNT(*)
INTO V_rec_cnt
FROM load_table;
IF V_rec_cnt > 0 THEN
-- table is not empty, process records . . .
What is the purpose?
Does the program really need to know how many records are in the table?
Or, is the intent just to make sure that the table is not empty?
SELECT COUNT(*)
INTO V_rec_cnt
FROM load_table
WHERE ROWNUM = 1;

25. Opens cursor to find out how many records will be returned
Another variation
SELECT empi, fcilty_id, immu_dt
, COUNT (*) OVER () rec_count
FROM immu_vaccinations
WHERE acct_no = ' '
DECLARE
V_rec_count :
CURSOR my_recs IS
( SELECT empi, fcilty_id, immu_dt
FROM immu_vaccinations
WHERE acct_no = ' ' )
recs_t IS TABLE OF my_recs%ROWTYPE;
v_recs recs_t;
BEGIN
OPEN my_recs;
FETCH my_recs BULK COLLECT INTO v_recs;
CLOSE my_recs;
IF v_recs.COUNT = 1 THEN
FOR j IN my_recs LOOP
<< processing to do if the cursor returned only one records >>
END LOOP;
ELSE
<< processing to do if the cursor returned multiple records >>
END IF;
END;
Use analytic function to collect the record count at the same time as query records
Opens cursor to find out how many records will be returned
Different logic for one record versus multiple records. Reexecutes the same query

26. Bug #3
Default Values for Parameters

27. Function to calculate age
Default value for second parameter means if no value is passed, then function will use sysdate
FUNCTION get_age_in_years
( p_birth_date IN DATE
, p_as_of_date IN DATE DEFAULT SYSDATE )
RETURN NUMBER IS
v_ret_val NUMBER;
BEGIN
v_ret_val := TRUNC( MONTHS_BETWEEN ( p_as_of_date, p_birth_date )/12);
RETURN v_ret_val;
END get_age_in_years;
BEGIN
dbms_output.put_line
( 'AGE=' || get_age_in_years ( DATE ' ' , DATE ' ' ) );
dbms_output.put_line ( 'AGE=' || get_age_in_years ( DATE ' ' ) );
END;
BEGIN
dbms_output.put_line
( 'AGE=' || get_age_in_years ( DATE ' ' , DATE ' ' ) );
dbms_output.put_line ( 'AGE=' || get_age_in_years ( DATE ' ' ) );
END; /
AGE=43
PL/SQL procedure successfully completed.
BEGIN
dbms_output.put_line
( 'AGE=' || get_age_in_years ( DATE ' ' , DATE ' ' ) );
END; /
BEGIN
dbms_output.put_line
( 'AGE=' || get_age_in_years ( DATE ' ' , DATE ' ' ) );
END; /
AGE=43
PL/SQL procedure successfully completed.

28. Parameter Defaults and NULL
DECLARE
v_from_date DATE;
v_to_date DATE;
BEGIN
v_from_date := DATE ' ';
dbms_output.put_line
( 'AGE=' || get_age_in_years ( v_from_date, v_to_date ) );
( 'AGE=' || get_age_in_years ( v_from_date ) );
END; /
AGE=
AGE=43
DECLARE
v_from_date DATE;
v_to_date DATE;
BEGIN
v_from_date := DATE ' ';
dbms_output.put_line
( 'AGE=' || get_age_in_years ( v_from_date, v_to_date ) );
( 'AGE=' || get_age_in_years ( v_from_date ) );
END; /
In the first call, a variable with a NULL value was passed to the second parameter.
In the second call, the second parameter was not referenced at all.
In the second call, the default value of the parameter was used by the function.

29. How can you avoid this?
If you need to make sure that the parameter is not null, use a variable
This is needed still. Why?
FUNCTION get_age_in_years
( p_birth_date IN DATE
, p_as_of_date IN DATE DEFAULT SYSDATE )
RETURN NUMBER IS
v_ret_val NUMBER;
v_as_of_date DATE;
BEGIN
v_as_of_date := NVL( p_as_of_date, SYSDATE );
v_ret_val := TRUNC( MONTHS_BETWEEN ( v_as_of_date, p_birth_date )/12);
RETURN v_ret_val;
END get_age_in_years;
Variable for param
NVL to handle NULL value

30. Calling With Function Fixed
DECLARE
v_from_date DATE;
v_to_date DATE;
BEGIN
v_from_date := DATE ' ';
dbms_output.put_line
( 'AGE=' || get_age_in_years ( v_from_date, v_to_date ) );
( 'AGE=' || get_age_in_years ( v_from_date ) );
END; /
AGE=43
DECLARE
v_from_date DATE;
v_to_date DATE;
BEGIN
v_from_date := DATE ' ';
dbms_output.put_line
( 'AGE=' || get_age_in_years ( v_from_date, v_to_date ) );
( 'AGE=' || get_age_in_years ( v_from_date ) );
END; /
Success!

31. Bug #4
Function returned without value

32. Function
FUNCTION get_age_description
( p_birth_date IN DATE
, p_as_of_date IN DATE )
RETURN VARCHAR2 IS
v_age NUMBER;
BEGIN
v_age := TRUNC( MONTHS_BETWEEN
( p_as_of_date, p_birth_date )/12);
IF v_age < 18 THEN
RETURN 'Minor';
ELSIF v_age = 18 THEN
RETURN 'Voting age';
ELSIF v_age = 21 THEN
RETURN 'Drinking age';
ELSIF v_age BETWEEN 22 AND 65 THEN
RETURN 'Adult';
ELSIF v_age > 66 THEN
RETURN 'Eligible for Medicare';
END IF;
END get_age_description;
SELECT get_age_description
( DATE ' ', SYSDATE ) AS test
FROM DUAL;
SELECT get_age_description
( DATE ' ', SYSDATE ) AS test
FROM DUAL; *
ERROR at line 1:
ORA-06503: PL/SQL: Function returned without value
ORA-06512: at "SCOTT.GET_AGE_DESCRIPTION", line 30
SELECT get_age_description
( DATE ' ', SYSDATE ) AS test
FROM DUAL;
TEST
Voting age
1 row selected.
SELECT get_age_description
( DATE ' ', SYSDATE ) AS test
FROM DUAL;
This error means that execution got all the way to the end of the function and never encountered a RETURN statement

33. 2nd attempt Introduction of a variable to hold RETURN value
FUNCTION get_age_description
( p_birth_date IN DATE
, p_as_of_date IN DATE )
RETURN VARCHAR2 IS
v_age NUMBER;
v_ret_val VARCHAR2(25);
BEGIN
v_age := TRUNC( MONTHS_BETWEEN
( p_as_of_date, p_birth_date )/12);
IF v_age < 18 THEN
v_ret_val := 'Minor';
ELSIF v_age = 18 THEN
v_ret_val := 'Voting age';
ELSIF v_age = 21 THEN
v_ret_val := 'Drinking age';
ELSIF v_age > 66 THEN
v_ret_val := 'Eligible for Medicare';
ELSIF v_age BETWEEN 22 AND 65 THEN
v_ret_val := 'Adult';
END IF;
RETURN v_ret_val;
END get_age_description;
Introduction of a variable to hold RETURN value
SELECT get_age_description
( DATE ' ', SYSDATE ) AS test
FROM DUAL;
TEST
1 row selected.
SELECT get_age_description
( DATE ' ', SYSDATE ) AS test
FROM DUAL;
This time, the function returned NULL
ELSE
One possible fix
Single point of RETURN from function

34. Using CASE
FUNCTION get_age_description
( p_birth_date IN DATE
, p_as_of_date IN DATE )
RETURN VARCHAR2 IS
v_age NUMBER;
v_ret_val VARCHAR2(25);
BEGIN
v_age := TRUNC( MONTHS_BETWEEN (
p_as_of_date, p_birth_date )/12);
CASE WHEN v_age < 18 THEN
v_ret_val := 'Minor';
WHEN v_age = 18 THEN
v_ret_val := 'Voting age';
WHEN v_age = 21 THEN
v_ret_val := 'Drinking age';
WHEN v_age > 66 THEN
v_ret_val := 'Eligible for Medicare';
WHEN v_age BETWEEN 22 AND 65 THEN
v_ret_val := 'Adult';
END CASE;
RETURN v_ret_val;
END get_age_description;
In any PLSQL development, when you do not expect an “ELSE”, use CASE instead of IF for tighter coding.
SELECT get_age_description
( DATE ' ', SYSDATE ) AS test
FROM DUAL;
SELECT get_age_description
( DATE ' ', SYSDATE ) AS test
FROM DUAL; *
ERROR at line 1:
ORA-06592: CASE not found while executing CASE statement
ORA-06512: at "SCOTT.GET_AGE_DESCRIPTION", line 13
Unlike IF /ELSIF, PLSQL CASE requires that one of the branches be executed

35. Bug #5
Declaration section exceptions

36. What will happen here? Division by zero here
DECLARE
x NUMBER :=10/0;
BEGIN
dbms_output.put_line('Successful run.');
EXCEPTION
WHEN zero_divide THEN
dbms_output.put_line('zero_divide exception handler');
WHEN OTHERS THEN
dbms_output.put_line('others exception handler');
END; /
Division by zero here
Two different handlers
Neither of the exception handlers was raised!
DECLARE *
ERROR at line 1:
ORA-01476: divisor is equal to zero
ORA-06512: at line 3

37. Handlers Gotchas The exception was raised in the “green” block
But, it was not handled in “green” block
It was handled in “blue” block
But, at least it was handled!
BEGIN
DECLARE
v NUMBER(1) := 10;
v:= 20;
EXCEPTION
WHEN OTHERS THEN
dbms_output.put_line ( 'Handler 1');
END;
dbms_output.put_line ( 'Handler 2');
Handler 2

38. What can you do?
Avoid variable assignment in declaration section when possible
Not possible with CONSTANT
Nest blocks in larger blocks so that errors can be handled

39. Bug #6
More FOR LOOP problems

40. The lower number must come first, or the loop is not executed
Loop Bugs
BEGIN
FOR i IN LOOP
dbms_output.put_line ( i );
END LOOP;
END;
No output.
Why?
BEGIN
FOR i IN LOOP
dbms_output.put_line ( i );
END LOOP;
END;
The lower number must come first, or the loop is not executed -5 -4 -3 -2 -1

41. Even with REVERSE, the lower number must come first
Loop Bugs
A backwards loop
BEGIN
FOR i IN REVERSE 5..1 LOOP
dbms_output.put_line ( i );
END LOOP;
END ;
Again: No output.
BEGIN
FOR i IN REVERSE 1..5 LOOP
dbms_output.put_line ( i );
END LOOP;
END ;
Even with REVERSE, the lower number must come first 5 4 3 2 1

42. FOR LOOP Endpoints i empno (1) 7369 (2) 7566 (3) 7788 (4) 7876 (5)
DECLARE
TYPE number_t IS TABLE OF NUMBER;
v_empnos number_t;
BEGIN
SELECT empno
BULK COLLECT INTO v_empnos
FROM scott.emp
WHERE deptno = 20;
FOR i IN v_empnos.FIRST..v_empnos.LAST
LOOP
-- Loop through records for additional processing
dbms_output.put_line ( v_empnos(i) );
END LOOP;
END; / i
empno
(1)
7369
(2)
7566
(3)
7788
(4)
7876
(5)
7902 1 5
7369
7566
7788
7876
7902
PL/SQL procedure successfully completed.

43. FOR LOOP Endpoints No emps in dept 40 i empno Empty array NULL NULL
DECLARE
TYPE number_t IS TABLE OF NUMBER;
v_empnos number_t;
BEGIN
SELECT empno
BULK COLLECT INTO v_empnos
FROM scott.emp
WHERE deptno = 40;
FOR i IN v_empnos.FIRST..v_empnos.LAST
LOOP
-- Loop through records for additional processing
dbms_output.put_line ( v_empnos(i) );
END LOOP;
END; /
No emps in
dept 40 i
empno
Empty array
NULL
NULL
DECLARE *
ERROR at line 1:
ORA-06502: PL/SQL: numeric or value error
ORA-06512: at line 10

44. Fix #1 When the array is empty, COUNT returns 0.
DECLARE
TYPE number_t IS TABLE OF NUMBER;
v_empnos number_t;
BEGIN
SELECT empno
BULK COLLECT INTO v_empnos
FROM scott.emp
WHERE deptno = 40;
FOR i IN 1..v_empnos.COUNT
LOOP
-- Loop through records for additional processing
dbms_output.put_line ( v_empnos(i) );
END LOOP;
END; /
When the array is empty,
COUNT returns 0.
It does not return NULL
FOR i IN 1..0 LOOP
Remember: If the second number is lower than the first number, the FOR LOOP does not execute.
PL/SQL procedure successfully completed.

45. Fix #2 Because it’s not a FOR LOOP, the variable MUST be declared.
TYPE number_t IS TABLE OF NUMBER;
v_empnos number_t;
i NUMBER;
BEGIN
SELECT empno
BULK COLLECT INTO v_empnos
FROM scott.emp
WHERE deptno = 40;
i := v_empnos.FIRST;
WHILE i IS NOT NULL
LOOP
-- Loop through records for additional processing
dbms_output.put_line ( v_empnos(i) );
i := v_empnos.NEXT (i);
END LOOP;
END; /
Because it’s not a
FOR LOOP, the variable MUST be declared.
If the array is empty, this function returns NULL
LOOP Exit mechanism
When this is called after the last record, it returns NULL, too
This is the only way to code this if the array is sparse
PL/SQL procedure successfully completed.

46. Bug #7
Implicit COMMIT

47. In case of load error, rollback
The set-up
Clear the table
Loop through records
EMP_MGR
EMP
Load
Transform
Clear
BEGIN
EXECUTE IMMEDIATE 'TRUNCATE TABLE scott.emp_mgr';
FOR rec IN ( SELECT e.ename AS ename
, m.ename AS mgrname
FROM scott.emp e JOIN scott.emp m
ON e.mgr = m.empno )
LOOP
INSERT INTO scott.emp_mgr
VALUES rec;
END LOOP;
COMMIT;
EXCEPTION WHEN OTHERS THEN
dbms_output.put_line ( SQLERRM );
ROLLBACK;
END;
In case of load error, rollback
Load
Script to set this up:
CREATE TABLE emp_mgr
( ename VARCHAR2(6), mgrname VARCHAR2(6));
INSERT INTO scott.emp
VALUES ( 7777, 'O''REILLY', 'CORPORAL', 7902, DATE ' ', 900, NULL, 10);
COMMIT;
DESC scott.emp_mgr
EMP_MGR
ENAME
VARCHAR2(6)
MGRNAME
Rollback

48. After the error, the table is empty. Something went wrong
ETL Run
SELECT COUNT(*) FROM scott.emp_mgr;
COUNT(*) 13
1 row selected.
INSERT INTO scott.emp
VALUES ( 7777, 'O''REILLY', 'CORPORAL'
, 7902, DATE ' ', 900
, NULL, 10);
1 row created.
BEGIN
EXECUTE IMMEDIATE 'TRUNCATE TABLE scott.emp_mgr';
FOR rec IN ( SELECT e.ename AS ename
, m.ename AS mgrname
FROM scott.emp e JOIN scott.emp m
ON e.mgr = m.empno )
LOOP
INSERT INTO scott.emp_mgr
VALUES rec;
END LOOP;
COMMIT;
EXCEPTION WHEN OTHERS THEN
dbms_output.put_line ( SQLERRM );
ROLLBACK;
END; /
ORA-12899: value too large for column "SCOTT"."EMP_MGR"."ENAME" (actual: 8, maximum: 6)
PL/SQL procedure successfully completed.
Now, run ETL procedure
After the error, the table is empty. Something went wrong
SELECT COUNT(*) FROM scott.emp_mgr;
COUNT(*)
1 row selected.

49. Why was the load table empty?
DDL causes implicit COMMIT
TRUNCATE TABLE…
CREATE INDEX…
Remember that EXECUTE IMMEDIATE… ?
This is Oracle database behavior
Not PLSQL

50. Bug Killers Review Checklist : FOR LOOP variables No_data_found
Parameter defaults
Function returned without value
Declaration section exceptions
More FOR LOOP issues
Implicit COMMIT

51. Thank-you!
Dan Stober
Questions? Comments?

52. Copyright
All material contained herein is owned by Daniel Stober, the author of this presentation. This presentation and the queries, examples, and original sample data may be shared with others for educational purposes only in the following circumstances:
That the person or organization sharing the information is not compensated, or
If shared in a circumstance with compensation, that the author has granted written permission to use this work
Using examples from this presentation, in whole or in part, in another work without proper source attribution constitutes plagiarism.
Use of this work implies acceptance of these terms