The document discusses SQL optimization techniques emphasizing simplicity and the importance of understanding the desired query output. It highlights common pitfalls such as datatype mismatches that lead to full scans and stresses the value of practice and continual learning in optimizing SQL performance. The author advocates for a careful balance between simplicity and effectiveness to achieve optimal results in SQL queries.

1. zen and the art of SQL optimization Karen Morton

4. Simplicity

5. “ Make everything as simple as possible but no simpler. ” Albert Einstein

8. “ Normally, we do not so much look at things as overlook them.” Alan Watts

9. simple vs simple-minded

10. Oracle 9.2.0.6 SELECT to_char( to_date(:B1,‘DD-MON-YYYY’)+1, ‘DD-MON-YYYY’ ) FROM dual;

11. What about its effect?

12. 32.9% % of total R

13. 1,087,770 # of executions

14. 3,263,033 # of LIOs

15. v_date_str := to_char( to_date( :B1,‘DD-MON-YYYY’ ) + 1, ‘ DD-MON-YYYY’ ) ;

16. Focus

17. ETCIBMVIPNASAFBI

18. ETC IBM VIP NASA FBI

19. SELECT rowid, load_no, load_status, manifest_no, manifest_date FROM cs_loads WHERE load_no = 552888 ; VARCHAR2(15) SELECT rowid, load_no, load_status, manifest_no, manifest_date FROM cs_loads WHERE load_no = 552888 ; datatype mismatch causes FULL SCAN SELECT rowid, load_no, load_status, manifest_no, manifest_date FROM cs_loads WHERE load_no =‘552888’;

20. SELECT rowid, load_no, load_status, manifest_no, manifest_date FROM cs_loads WHERE load_no = :B1 ;

21. Keys to Optimizing SQL

22. Tune the question, not the query.

23. What output should the query provide?

24. What special conditions need to be handled?

25. “ If you don’t know where you are going, you’ll end up somewhere else.” Yogi Berra

26. Reduce. Reuse.

27. Decrease row source sizes quickly

28. Access objects once and reuse the result set

29. “ Not enough gets said about the importance of abandoning crap.” - Ira Glass

30. Practice.

31. Never stop learning

32. Stay connected

33. Think in sets

34. Test Test Test (then test again)

36. “ Practice, practice, practice. Until it becomes your practice.” Unknown

37. Going Zen

38. 1

39. SELECT invoice_id, distribution_line_number FROM ap.ap_invoice_distributions_all ap2 WHERE ap2.project_id > 0 AND ap2.pa_addition_flag = 'T' MINUS SELECT invoice_id, distribution_line_number FROM ap.ap_invoice_distributions_all ap, pa.pa_cost_distribution_lines_all pa WHERE ap.project_id > 0 AND ap.pa_addition_flag = 'T' AND pa.system_reference2 IS NOT NULL AND TO_NUMBER(pa.system_reference2) = ap.invoice_id AND TO_NUMBER(pa.system_reference3) = ap.distribution_line_number ORDER BY invoice_id; Elapsed Time LIO Blocks PIO Blocks Total Rows ------------ ---------- ---------- ---------- 00:00:20.09 60,941 57,116 6

40. SELECT invoice_id, distribution_line_number FROM (SELECT invoice_id, distribution_line_number, system_reference2, system_reference3 FROM ap.ap_invoice_distributions_all ap, (SELECT TO_NUMBER(system_reference2) system_reference2, TO_NUMBER(system_reference3) system_reference3 FROM pa.pa_cost_distribution_lines_all WHERE system_reference2 IS NOT NULL) WHERE system_reference2 (+) = ap.invoice_id AND system_reference3 (+) = ap.distribution_line_number AND ap.project_id > 0 AND ap.pa_addition_flag = 'T' ) WHERE system_reference2 IS NULL AND system_reference3 IS NULL ORDER BY invoice_id; Elapsed Time LIO Blocks PIO Blocks Total Rows ------------ ---------- ---------- ---------- 00:00:03.09 1,824 453 6

41. 2

42. SELECT t.* FROM RMS.tasks t, RMS.status s WHERE t.status_id = s.id AND (EXISTS ( SELECT null FROM RMS.tasks ta, RMS.resources r WHERE t.id = ta.parent_task_id AND ta.project_code = :p AND ta.task_type_code = 'A' AND ta.resource_id = r.id AND r.reporting_id = :r ) OR (t.project_code = :p AND t.task_type_code = 'T') ); Elapsed Time LIO Blocks PIO Blocks Total Rows ------------ ---------- ---------- ---------- 00:00:09.50 287,330 992 3

43. SELECT t.* FROM RMS.tasks t, RMS.status s WHERE t.status_id = s.id AND EXISTS (SELECT null FROM RMS.tasks ta,RMS.resources r WHERE t.id = ta.parent_task_id AND ta.project_code = :p AND ta.task_type_code = 'A' AND ta.resource_id = r.id AND r.reporting_id = :r ) UNION SELECT t.* FROM RMS.tasks t, RMS.status s WHERE t.status_id = s.id AND t.id IN (SELECT t.parent_task_id FROM RMS.tasks t, RMS.status s WHERE t.status_id = s.id AND EXISTS (SELECT null FROM RMS.tasks ta, RMS.resources r WHERE t.id = ta.parent_task_id AND ta.project_code = :p AND ta.task_type_code = 'A' AND ta.resource_id = r.id AND r.reporting_id = :r ); Elapsed Time LIO Blocks PIO Blocks Total Rows ------------ ---------- ---------- ---------- 00:00:00.01 128 0 3

44. 3

45. SELECT J.emplid, J.empl_rcd, J.effdt, J.effseq FROM PS_JOB J WHERE J.effdt = (SELECT MAX(effdt) FROM PS_JOB WHERE emplid = J.emplid AND empl_rcd = J.empl_rcd AND effdt <= SYSDATE ) AND J. effseq = (SELECT MAX(effseq) FROM PS_JOB WHERE emplid = J.emplid AND empl_rcd = J.empl_rcd AND effdt = J.effdt ) ; Elapsed Time LIO Blocks PIO Blocks Total Rows ------------ ---------- ---------- ---------- 00:00:08.04 337,908 0 30,107

46. SELECT J.emplid, J.empl_rcd, J.effdt, J.effseq FROM (SELECT J.emplid, J.empl_rcd, J.effdt, J.effseq, MAX(J.effdt) OVER (PARTITION BY J.emplid, J.empl_rcd ) max_effdt, LAST_VALUE(J.effseq) OVER (PARTITION BY J.emplid, J.empl_rcd ORDER BY J.efdt, J.effseq ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING ) max_effseq FROM PS_JOB J WHERE J.effdt <= SYSDATE ) J WHERE J.effdt = J.max_effdt AND J.effseq = J.max_effseq; Elapsed Time LIO Blocks PIO Blocks Total Rows ------------ ---------- ---------- ---------- 00:00:00.44 1,009 0 30,107

47. 4

48. SELECT utrsotp_desc FROM utrsotp, ucbsvco WHERE ucbsvco_sotp_code = utrsotp_code AND ucbsvco_dispatch_date = (SELECT MAX(ucbsvco_dispatch_date) FROM ucbsvco WHERE ucbsvco_cust_code = 1320908 AND ucbsvco_prem_code = '507601' AND ucbsvco_stus_code = 'C' AND ucbsvco_dispatch_ind IS NOT NULL) AND ucbsvco_stus_code = 'C' AND ucbsvco_dispatch_ind IS NOT NULL Elapsed Time LIO Blocks PIO Blocks Total Rows ------------ ---------- ---------- ---------- 00:00:20.16 106,693 0 1

49. SELECT utrsotp_desc FROM utrsotp, (SELECT ucbsvco_sotp_code, ucbsvco_dispatch_date, MAX(ucbsvco_dispatch_date) OVER(PARTITION BY ucbsvco_cust_code, ucbsvco_prem_code) max_dispatch_dt FROM ucbsvco WHERE ucbsvco_cust_code = 1320908 AND ucbsvco_prem_code = '507601' AND ucbsvco_stus_code = 'C' AND ucbsvco_dispatch_ind IS NOT NULL) svco WHERE svco.ucbsvco_dispatch_date = svco.max_dispatch_dt AND svco.ucbsvco_sotp_code = utrsotp_code Elapsed Time LIO Blocks PIO Blocks Total Rows ------------ ---------- ---------- ---------- 00:00:00.18 15 0 1

51. Simplicity is powerful…

52. … but it is neither simple nor easy to achieve.

53. It is obtained through the careful reduction of the nonessential.

54. While simplicity is the goal…

55. … it is possible to be “too simple.”

56. Your job is to find the balance most appropriate to your situation.

57. Thank You

58. http://www.method-r.com http://karenmorton.blogspot.com [email_address]