After completing this unit, you should be able to: Use inner joins to retrieve data from more than one table

Transcription

1 JOIN

2 Objectives After completing this unit, you should be able to: Use inner joins to retrieve data from more than one table Use outer joins complementing inner joins

3 Sample Tables for Unit EMPLOYEE EMPNO LASTNAME WORKDEPT SALARY HAAS A KWAN O'CONNELL QUINTANA NICHOLLS WILSON A DEPTNO A00 DEPTNAME SPIFFY COMPUTER SERVICE DIV. MGRNO DEPARTMENT D01 DEVELOPMENT CENTER PROJECT PROJNO AD3100 IF1000 PROJNAME ADMIN SERVICES QUERY SERVICES DEPTNO D01 RESPEMP IF2000 USER EDUCATION

4 Join SELECT EMPNO, LASTNAME, DEPTNO, DEPTNAME, DEPARTMENT WHERE WORKDEPT = DEPTNO EMPNO LASTNAME DEPTNO DEPTNAME HAAS A00 SPIFFY COMPUTER SERVICE DIV O'CONNELL KWAN NICHOLLS QUINTANA A00 SPIFFY COMPUTER SERVICE DIV. RESULT

5 Inner Join SELECT EMPNO, LASTNAME, DEPTNO, DEPTNAME INNER JOIN DEPARTMENT EMPNO LASTNAME DEPTNO DEPTNAME HAAS A00 SPIFFY COMPUTER SERVICE DIV O'CONNELL A00 SPIFFY COMPUTER SERVICE DIV KWAN NICHOLLS QUINTANA RESULT

6 Right Outer Join SELECT EMPNO, LASTNAME, DEPTNO, DEPTNAME RIGHT OUTER JOIN DEPARTMENT EMPNO LASTNAME DEPTNO DEPTNAME HAAS O'CONNELL KWAN QUINTANA A00 A00 SPIFFY COMPUTER SERVICE DIV. SPIFFY COMPUTER SERVICE DIV RESULT NICHOLLS D01 DEVELOPMENT CENTER

7 Left Outer Join SELECT EMPNO, LASTNAME, DEPTNO, DEPTNAME LEFT OUTER JOIN DEPARTMENT EMPNO LASTNAME DEPTNO DEPTNAME HAAS A00 SPIFFY COMPUTER SERVICE DIV KWAN O'CONNELL A00 SPIFFY COMPUTER SERVICE DIV QUINTANA NICHOLLS WILSON RESULT

8 Full Outer Join SELECT EMPNO, LASTNAME, DEPTNO, DEPTNAME FULL OUTER JOIN DEPARTMENT EMPNO LASTNAME DEPTNO DEPTNAME O'CONNELL A00 SPIFFY COMPUTER SERVICE DIV HAAS A00 SPIFFY COMPUTER SERVICE DIV KWAN QUINTANA NICHOLLS D01 DEVELOPMENT CENTER WILSON RESULT

9 Joins of More Than Two Tables SELECT PROJNO,PROJNAME, P.DEPTNO, MGRNO, LASTNAME AS MGRNAME FROM PROJECT P INNER JOIN DEPARTMENT D ON P.DEPTNO = D.DEPTNO LEFT OUTER JOIN EMPLOYEE ON MGRNO = EMPNO PROJNO PROJNAME DEPTNO MGRNO MGRNAME IF2000 USER EDUCATION KWAN IF1000 QUERY SERVICES KWAN AD3100 ADMIN SERVICES D01 RESULT Left and right joins are not symmertrical.

10 Joins and Local Predicates (Part 1) SELECT EMPNO, LASTNAME, SALARY, DEPTNO, DEPTNAME FULL OUTER JOIN DEPARTMENT WHERE SALARY > AND DEPTNAME LIKE '%CENTER%' EMPNO LASTNAME WORKDEPT SALARY DEPTNO DEPTNAME O'CONNELL A HAAS A KWAN QUINTANA NICHOLLS MGRNO A00 SPIFFY COMPUTER SERVICE DIV A00 SPIFFY COMPUTER SERVICE DIV D01 DEVELOPMENT CENTER WILSON INTERMEDIATE RESULT TABLE

11 Joins and Local Predicates (Part 2) SELECT EMPNO, LASTNAME, SALARY, DEPTNO, DEPTNAME FULL OUTER JOIN DEPARTMENT EMPNO LASTNAME WORKDEPT SALARY DEPTNO DEPTNAME O'CONNELL A HAAS A KWAN QUINTANA NICHOLLS MGRNO A00 SPIFFY COMPUTER SERVICE DIV A00 SPIFFY COMPUTER SERVICE DIV D01 DEVELOPMENT CENTER WILSON WHERE SALARY > AND DEPTNAME LIKE '%CENTER%' EMPNO LASTNAME SALARY DEPTNO DEPTNAME KWAN

12 Joins and Additional Join Predicates SELECT EMPNO, LASTNAME, SALARY,WORKDEPT, DEPTNO, CHAR(DEPTNAME,11) AS DEPTNAME FULL OUTER JOIN DEPARTMENT AND SALARY > AND DEPTNAME LIKE '%CENTER%' EMPNO LASTNAME SALARY WORKDEPT DEPTNO DEPTNAME O'CONNELL HAAS A KWAN INFORMATION QUINTANA NICHOLLS D01 DEVELOPMENT WILSON A00 SPIFFY COM

13 Summary Now that you have completed this unit, you should be able to: Use inner joins to retrieve data from more than one table Use outer joins complementing inner joins