DB2 SQL for the 21 st Century: Overlooked Enhancements. David Simpson

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1 DB2 SQL for the 21 st Century: Overlooked Enhancements David Simpson

2 Themis Education Most complete DB2 Curriculum in the industry Offerings include a complete mainframe curriculum in addition to Oracle, Java,.NET, Linux, UNIX, etc. Training Venues: At your facility for groups Public enrollment at various locations in the USA Distance learning public enrollment with live instructors. Webinars: Visit for upcoming schedule and replays of past webinars and to download today s slides. Coming in March: John Mullins 20 Essential Oracle SQL and PL/SQL Tuning Tips Me Part 2 of this presentation

3 David Simpson David Simpson is currently the Vice President of Themis Inc. He teaches courses on SQL, Application Programming, Database Administration as well as optimization, performance and tuning. He also installs and maintains the database systems used for training at Themis and works with our network of instructors to deliver high quality training solutions to our customers worldwide. Since 1993 David has worked as a developer and DBA in support of very large transactional and business intelligence systems. David is a certified DB2 DBA on both z/os and LUW. David was voted Best User Speaker and Best Overall Speaker at IDUG North America He was also voted Best User Speaker at IDUG Europe 2006 and is a member of the IDUG Speakers Hall of Fame. David is also an IBM Champion for Information Management. dsimpson@themisinc.com

4 This material comes from Themis course: DB1041: Advanced SQL for DB2 Description March 14 Offering

5 Table Expressions (V4 & V8)

6 Nested Table Expressions What are they? - Sometimes called inline views - Sometimes called derived tables - They are a SELECT statement within a FROM clause - A virtual table created only for the duration of the query - They are not documented in the system catalog - They are an SQL fullselect enclosed in parentheses and followed by a correlation name - They bypass the need to predefine a table of data that an application currently does not have

7 The Sample EMP Table EMPNO FIRSTNME LASTNAME DEPTNO SALARY BONUS CHRISTINE HAAS A CHRISTINE HAAS A VINCENZO LUCCHESI A SEAN O'CONNELL A MICHAEL THOMPSON B SALLY KWAN C DOLORES QUINTANA C HEATHER NICHOLLS C IRVING STERN D BRUCE ADAMSON D ELIZABETH PIANKA D MASATOSHI YOSHIMURA D MARILYN SCOUTTEN D JAMES WALKER D DAVID BROWN D WILLIAM JONES D JENNIFER LUTZ D

8 NTE Example Provide a report that shows the following: Each employee s number, last name, salary, department number and the average salary of the department they work in. SELECT E.EMPNO, E.LASTNAME, E.SALARY, E.DEPTNO, X.AVG_SAL FROM EMP E, (SELECT DEPTNO, AVG(SALARY) AS AVG_SAL FROM EMP GROUP BY DEPTNO) X WHERE E.DEPTNO = X.DEPTNO *** X is the Nested Table Expression name.

9 The Result EMPNO LASTNAME SALARY DEPTNO AVG_SAL HAAS A HAAS A LUCCHESI A O'CONNELL A THOMPSON B KWAN C QUINTANA C NICHOLLS C STERN D ADAMSON D PIANKA D YOSHIMURA D SCOUTTEN D WALKER D BROWN D JONES D LUTZ D

10 Did You Know? This is the previous example could also be coded as a Common Table Expression (CTE). WITH DEPTAVG AS (SELECT DEPTNO, AVG(SALARY) AS AVG_SAL FROM EMP GROUP BY DEPTNO) SELECT E.EMPNO, E.LASTNAME, E.SALARY, E.DEPTNO, DA.AVG_SAL FROM EMP E, DEPTAVG DA WHERE E.DEPTNO = DA.DEPTNO

11 Differences Between CTE and NTE A Common Table Expression can only be defined at the beginning of a query, but once defined, can be used in any From clause in the query. A Nested Table Expression can be placed in any FROM clause in the query, but must be re-defined each time it is used.

12 Problem Return the department number and the total payroll for the department that has the highest payroll. Payroll will be defined as the sum of all salaries and bonuses for the department.

13 Solution #1: Use a View CREATE VIEW DEPTPAY (DEPTNO, DEPT_TOT) AS SELECT DEPTNO, SUM(SALARY + BONUS) FROM EMP GROUP BY DEPTNO SELECT DEPTNO, DEPT_TOT FROM DEPTPAY WHERE DEPT_TOT = (SELECT MAX(DEPT_TOT) FROM DEPTPAY) DEPTNO DEPT_TOT D

14 Solution #2: Use Nested Table Expressions SELECT DEPTNO, DEPT_TOT FROM (SELECT DEPTNO, SUM(SALARY + BONUS) AS DEPT_TOT FROM EMP GROUP BY DEPTNO) DEPTPAY WHERE DEPT_TOT = (SELECT MAX(TOT2) FROM (SELECT DEPTNO, SUM(SALARY + BONUS) TOT2 FROM EMP GROUP BY DEPTNO) DEPTPAY2 )

15 Solution #3: Use a Common Table Expression WITH DEPTPAY AS (SELECT DEPTNO, SUM(SALARY + BONUS) AS DEPT_TOT FROM EMP GROUP BY DEPTNO) SELECT DEPTNO, DEPT_TOT FROM DEPTPAY WHERE DEPT_TOT = (SELECT MAX(DEPT_TOT) FROM DEPTPAY)

16 Multiple Common Table Expressions WITH X AS (SELECT D.DEPTNO, COUNT(E.DEPTNO) AS NUM_EMPS FROM THEMIS90.DEPT D LEFT JOIN THEMIS90.EMP E ON D.DEPTNO = E.DEPTNO GROUP BY D.DEPTNO), Y AS (SELECT D.DEPTNO, COUNT(P.DEPTNO) AS NUM_PROJS FROM THEMIS90.DEPT D LEFT JOIN THEMIS90.PROJ P ON D.DEPTNO = P.DEPTNO GROUP BY D.DEPTNO) SELECT X.DEPTNO, X.NUM_EMPS, Y.NUM_PROJS FROM X, Y WHERE X.DEPTNO = Y.DEPTNO ;

17 Recursive SQL (V8)

18 PROJ Table (partial data) Recursive Data PROJNO PROJNAME MAJPROJ AD3100 ADMIN SERVICES NULL AD3110 GENERAL AD SYSTEMS AD3100 AD3111 PAYROLL PROGRAMMING AD3110 AD3112 PERSONNEL PROGRAMMG AD3110 AD3113 ACCOUNT.PROGRAMMING AD3110 IF1000 QUERY SERVICES NULL IF2000 USER EDUCATION NULL MA2100 WELD LINE AUTOMATION AD3110 MA2110 W L PROGRAMMING MA2100 MA2111 W L PROGRAM DESIGN MA2110 MA2112 W L ROBOT DESIGN MA2110 MA2113 W L PROD CONT PROGS MA2110 OP1000 OPERATION SUPPORT NULL OP1010 OPERATION OP1000 OP2000 GEN SYSTEMS SERVICES NULL OP2010 SYSTEMS SUPPORT OP2000 OP2011 SCP SYSTEMS SUPPORT OP2010 OP2012 APPLICATIONS SUPPORT OP2010 OP2013 DB/DC SUPPORT OP2010 PL2100 WELD LINE PLANNING MA2100 Find all Projects under AD3100

19 Solution #1: Join SELECT L1.PROJNO, L2.PROJNO FROM PROJ L1 INNER JOIN PROJ L2 ON L1.PROJNO = L2.MAJPROJ WHERE L1.MAJPROJ = 'AD3100' Find all Projects under AD3100 PROJNO AD3110 AD3110 AD3110 AD3110 PROJNO AD3111 AD3112 AD3113 MA2100

20 Solution #1: Join SELECT L1.PROJNO, L2.PROJNO, L3.PROJNO FROM PROJ L1 INNER JOIN PROJ L2 ON L1.PROJNO = L2.MAJPROJ LEFT JOIN PROJ L3 ON L2.PROJNO = L3.MAJPROJ WHERE L1.MAJPROJ = 'AD3100' PROJNO PROJNO PROJNO AD3110 MA2100 MA2110 AD3110 MA2100 PL2100 AD3110 AD3113 NULL AD3110 AD3111 NULL AD3110 AD3112 NULL

21 Solution #2: Recursive SQL WITH PROJECTS (PNO, PNAME) AS (SELECT PROJNO, PROJNAME FROM PROJ WHERE PROJNO = 'AD3100' UNION ALL SELECT P.PROJNO, P.PROJNAME FROM PROJ P JOIN PROJECTS ON P.MAJPROJ = PROJECTS.PNO ) SELECT PNO, PNAME FROM PROJECTS Final SELECT ORDER BY PNO Initial SELECT Recursive SELECT

22 The Result PNO PNAME MPROJ LVL AD3100 ADMIN SERVICES NULL 1 AD3110 GENERAL AD SYSTEMS AD AD3111 PAYROLL PROGRAMMING AD AD3112 PERSONNEL PROGRAMMG AD AD3113 ACCOUNT PROGRAMMING AD MA2100 WELD LINE AUTOMATION AD MA2110 W L PROGRAMMING MA MA2111 W L PROGRAM DESIGN MA MA2112 W L ROBOT DESIGN MA MA2113 W L PROD CONT PROGS MA PL2100 WELD LINE PLANNING MA2100 4

23 Avoiding Loops WITH PROJECTS (PNO, PNAME, LVL) AS (SELECT PROJNO, PROJNAME, 1 AS LVL FROM PROJ WHERE PROJNO = 'AD3100' UNION ALL SELECT P.PROJNO, P.PROJNAME, PROJECTS.LVL + 1 FROM PROJ P JOIN PROJECTS ON P.MAJPROJ = PROJECTS.PNO WHERE PROJECTS.LVL < 100 ) SELECT PNO, PNAME, LVL FROM PROJECTS ORDER BY PNO

24 Part 2 on March 23 Built-in Functions for Ranking & Numbering Advanced Aggregation with SQL??? Register at