Oracle PL/SQL Best Practices Part 1. John Mullins

Transcription

1 Oracle PLSQL Best Practices Part 1 John Mullins jmullins@themisinc.com

2 Presenter John Mullins Themis Inc. 30+ years of Oracle experience Oracle Certified Professional DBA Certified Technical Trainer Over 300 classes taught

3 Themis Inc. More than 20 years in the industry More than 90,000 students have attended a Themis training event Courses: DB2, SQL Server, Oracle, Unix, Linux, Java, Web Development,.NET and many more

4 Related Themis Courses Introduction to Oracle PLSQL Programming June 26 Oracle Advanced PLSQL Programming June 29 Troubleshooting, Debugging and Tuning Oracle PLSQL Programs May 8, 2017

5 Webinar Objectives To become familiar with suggested best practices when coding Oracle PLSQL programs

6 Instead of: v_amount NUMBER (12,2) := 'A123'; IF v_amount > 0 THEN dbms_output.put_line ('OK'); END IF; EXCEPTION WHEN others THEN dbms_output.put_line ('Error HANDLED'); * ERROR at line 1: ORA-06502: PLSQL: numeric or value error: character to number conversion error ORA-06512: at line 2

7 Do: v_amount NUMBER (12,2); v_amount := 'A123'; IF v_amount > 0 THEN dbms_output.put_line ('OK'); END IF; EXCEPTION WHEN others THEN dbms_output.put_line ('Error HANDLED'); Error HANDLED PLSQL procedure successfully completed.

8 Instead of: CURSOR r1 IS SELECT last_name, department_name, salary FROM employee e, department d, employee_private ep WHERE e.department_id = d.department_id AND e.employee_id = ep.employee_id FOR UPDATE; FOR v_emp_rec IN r1 LOOP IF v_emp_rec.salary < THEN UPDATE employee_private SET salary = salary * 1.10 WHERE CURRENT OF r1; END IF; END LOOP; COMMIT;

9 Do: CURSOR r1 IS SELECT last_name, department_name, salary FROM employee e, department d, employee_private ep WHERE e.department_id = d.department_id AND e.employee_id = ep.employee_id FOR UPDATE OF ep.salary; FOR v_emp_rec IN r1 LOOP IF v_emp_rec.salary < THEN UPDATE employee_private SET salary = salary * 1.10 WHERE CURRENT OF r1; END IF; END LOOP; COMMIT;

10 Instead of: v_ename VARCHAR2(20);...

11 Do: v_ename emp.ename%type; v_emp_rec emp%rowtype;...

12 Instead of: v_sysdate DATE; SELECT sysdate INTO v_sysdate FROM dual;...

13 Do: v_sysdate DATE; v_sysdate := SYSDATE;...

14 Also Consider using SELECT BULK COLLECT and FORALL type statements to reduce context switches. SELECT order_id, order_total BULK COLLECT INTO v_order_ids, v_order_totals FROM product_order; FORALL i IN 1..v_order_ids.COUNT UPDATE product_order SET order_total = v_order_totals(i)-(v_order_totals(i)*.10) WHERE order_id = v_order_ids(i);

15 Instead of: TYPE atype IS TABLE OF number INDEX BY binary_integer; v_numbers atype; i NUMBER; v_numbers(1) := 100; v_numbers(5) := 500; i := v_numbers.first; WHILE i IS NOT NULL LOOP dbms_output.put_line (v_numbers(i)); i := i + 1; END LOOP; 100 * ERROR at line 1: ORA-01403: no data found ORA-06512: at line 11

16 Do: TYPE atype IS TABLE OF number INDEX BY binary_integer; v_numbers atype; i NUMBER; v_numbers(1) := 100; v_numbers(5) := 500; i := v_numbers.first; WHILE i IS NOT NULL LOOP dbms_output.put_line (v_numbers(i)); i := v_numbers.next(i); END LOOP; PLSQL procedure successfully completed.

17 Instead of: INSERT INTO department VALUES (88,'HR',44500); COMMIT; EXCEPTION WHEN others THEN dbms_output.put_line (SQLCODE);

18 Do: v_2291_error EXCEPTION; PRAGMA EXCEPTION_INIT (v_2291_error, -2291); INSERT INTO department VALUES (88,'HR',44500); COMMIT; EXCEPTION WHEN v_2291_error THEN dbms_output.put_line (SQLCODE);

19 Instead of: TYPE v_nums IS TABLE of employee_private.salary%type INDEX BY binary_integer; v_new_sals v_nums; UPDATE employee_private SET salary = salary * 1.10; --- SELECT salary BULK COLLECT INTO v_new_sals FROM employee_private;

20 Do: TYPE v_nums IS TABLE of employee_private.salary%type INDEX BY binary_integer; v_new_sals v_nums; UPDATE employee_private SET salary = salary * 1.10 RETURNING salary BULK COLLECT INTO v_new_sals; ---

21 Naming Conventions Use standard naming conventions and standard abbreviations for naming: Variable Names Parameter Names Cursors Types Programs and Packages

22 Summary Following best practices helps promote consistent, reliable, readable, easier to maintain PLSQL code along with possible performance gains Questions?

23 Upcoming Webinars Enhanced System-Period Temporal Tables on DB2 for zos Thursday April 27 11:30am ET

24 For More Information Visit the Themis web site John Caccavale To get a copy of the presentation: Thank you for attending. Have a good day.