Carl Dudley – University of Wolverhampton 1 Oracle Join Techniques Carl Dudley University of...

Carl Dudley – University of Wolverhampton 1

Oracle Join Techniques

Carl Dudley

University of Wolverhampton, UK

Oracle ACE Director

[email protected]

Introduction

ANSI and Oracle Joins

Two-way Outer Joins

Join and Filter Conditions

Chaining on the Outer Join

Hash Join Trees

Anti Joins and Semi Joins

Lateral Joins

Nested Loops Joins

Join Elimination

2Carl Dudley – University of Wolverhampton

Working with Oracle since 1986

Oracle DBA - OCP Oracle7, 8, 9, 10

Oracle DBA of the Year – 2002

Oracle ACE Director

Beta tester – Oracle8, 9, 10, 11, 12

Regular Presenter at Oracle Conferences

Consultant and Trainer

Technical Editor for a number of Oracle texts

UK Oracle User Group Official

Member of IOUC

Day job – University of Wolverhampton, UK

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO----- ---------- --------- ----- ----------- ----- ----- ------ 7934 MILLER CLERK 7782 23-JAN-1982 1300 10 7782 CLARK MANAGER 7839 09-JUN-1981 2450 10 7839 KING PRESIDENT 17-NOV-1981 5000 10 7369 SMITH CLERK 7902 17-DEC-1980 800 20 7876 ADAMS CLERK 7788 12-JAN-1983 1100 20 7566 JONES MANAGER 7839 02-APR-1981 2975 20 7902 FORD ANALYST 7566 03-DEC-1981 3000 20 7788 SCOTT ANALYST 7566 09-DEC-1982 3000 20 7900 JAMES CLERK 7698 03-DEC-1981 950 30 7521 WARD SALESMAN 7698 22-FEB-1981 1250 500 30 7654 MARTIN SALESMAN 7698 28-SEP-1981 1250 1400 30 7844 TURNER SALESMAN 7698 08-SEP-1981 1500 0 30 7499 ALLEN SALESMAN 7698 20-FEB-1981 1600 300 30 7698 BLAKE MANAGER 7839 01-MAY-1981 2850 30

DEPTNO DNAME LOC------ -------------- -------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON

dept

emp

The emp and dept Tables


ANSI Joins

ANSI defined join syntax in ANSI SQL2 Standard (1992)— Oracle finally fully implemented this syntax in Oracle9i

Types of joins specified by additional keywords

INNER JOIN

OUTER JOIN (LEFT RIGHT FULL)

CROSS JOIN

UNION JOIN (not supported by Oracle)


Inner Joins – ANSI and Oracle Syntax

Equivalent ANSI – based joins

SELECT ename,dname,dept.deptnoFROM emp JOIN dept ON dept.deptno = empa.deptno;

SELECT ename,dname,deptnoFROM emp NATURAL JOIN deptUSING (deptno);

— Note the absence of the table qualifier for deptno in some of the examples

Equivalent Oracle join

SELECT ename,dname,dept.deptnoFROM emp,dept WHERE emp.deptno = dept.deptno;

SELECT ename,dname,deptnoFROM emp NATURAL JOIN dept;


Not in common use and Oracle has no support but can be simulated

— Number of columns in each select clause must match

— Use NULLs to pad out the number of columns

Union Join

SELECT o.*, NULL,...,NULL FROM orders oUNION SELECT NULL,...,NULL, l.* FROM line_items l

OCOL1 OCOL2 LCOL1 LCOL2----- ----- ----- -----11111 AAAAA22222 BBBBB33333 CCCCC 88888 XXXXX 99999 YYYYY

Expected output

The Join Condition

SELECT ename,dname,dept.deptnoFROM emp JOIN dept;

ORA-00905: missing keyword

But join condition does not have to make any sense

— Could cause cartesian products

— Oracle join syntax has no protection

Join condition (ON clause) must be included ― Helps safeguard against inadvertant cartesian products

SELECT ename,dname,dept.deptnoFROM emp JOIN deptON emp.empno = emp.empno;


Multi-table Joins

If several tables are to be joined

— Use a step-wise process by first joining two of the tables

— Then add a further JOIN keyword to join to the third table

— Repeat this for each subsequent table

— Each join may have its own condition(s)

— The joins may be of different types

SELECT emp.empno ,emp.ename ,dept.loc ,proj.pnameFROM empJOIN deptON emp.deptno = dept.deptnoJOIN projON emp.proj_id = proj.proj_id;


LEFT and RIGHT Outer Joins

The driving table is specified with LEFT or RIGHT— This table will have all its rows included— Dummy NULL rows may be included from the other table

Refers to placement of the table name WITHIN the FROM ... JOIN clause

The following join clauses are all equivalent

FROM emp,dept

WHERE emp.deptno(+) = dept.deptno

FROM dept LEFT OUTER JOIN emp

ON emp.deptno = dept.deptno

FROM emp RIGHT OUTER JOIN dept

ON emp.deptno = dept.deptno


Modified Employee Data

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO----- ------ -------- ----- ----------- ---- ----- ------- 7782 CLARK MANAGER 7839 09-JUN-1981 2450 10 7788 SCOTT ANALYST 7566 19-APR-1987 3000 20 7844 TURNER SALESMAN 7698 08-SEP-1981 1500 0 30 7499 ALLEN SAlESMAN 7698 20-FEB-1981 1600 300 30 7902 FORD ANALYST 7566 03-DEC-1981 3000 20 1111 EXTRA CEO 01-JAN-1999 500

DEPTNO DNAME LOC------- ---------- -------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON

empa

dept


RIGHT Outer Joins

ENAME DNAME DEPTNO------- ------------ ------CLARK ACCOUNTING 10SCOTT RESEARCH 20TURNER SALES 30FORD RESEARCH 20ALLEN SALES 30 OPERATIONS 40

SELECT ename,dname,dept.deptnoFROM empa RIGHT OUTER JOIN dept ON empa.deptno = dept.deptno;

SELECT ename,dname,dept.deptnoFROM empa,dept WHERE dept.deptno = emp.deptno(+);

Equivalent Oracle join statement


LEFT Outer Joins

ENAME DNAME DEPTNO------- ------------ ------CLARK ACCOUNTING 10SCOTT RESEARCH 20TURNER SALES 30FORD RESEARCH 20ALLEN SALES 30EXTRA

SELECT ename,dname,dept.deptnoFROM empa LEFT OUTER JOIN deptON empa.deptno = dept.deptno;

SELECT ename,dname,dept.deptnoFROM empa, dept WHERE dept.deptno(+) = empa.deptno;

Equivalent Oracle join statement


FULL Outer Joins

ENAME DNAME D_DEPTNO E_DEPTNO------- ------------ -------- --------CLARK ACCOUNTING 10 10SCOTT RESEARCH 20 20TURNER SALES 30 30FORD RESEARCH 20 20ALLEN SALES 30 30EXTRA OPERATIONS 40

SELECT ename,dname,dept.deptno d_deptno, empa.deptno e_deptnoFROM empa FULL OUTER JOIN dept ON empa.deptno = dept.deptno;

SELECT ename,dname,dept.deptno,empa.deptnoFROM empa, dept WHERE dept.deptno(+) = empa.deptno(+);

Equivalent (ILLEGAL) Oracle join statement

All rows included from both tables


FULL OUTER JOIN – Oracle11g

Oracle now performs a 'NATIVE' full outer join

SELECT ename ,dnameFROM empa e FULL OUTER JOIN dept d ON e.deptno = d.deptno;

---------------------------------------------------------------| Id | Operation | Name |Rows |Bytes |Cost(%CPU---------------------------------------------------------------| 0| SELECT STATEMENT | | 15 | 240 | 7 (15| 1| VIEW | VW_FOJ_0 | 15 | 240 | 7 (15|* 2| HASH JOIN FULL OUTER| | 15 | 330 | 7 (15| 3| TABLE ACCESS FULL | DEPT | 4 | 52 | 3 (0| 4| TABLE ACCESS FULL | EMPA | 14 | 126 | 3 (0---------------------------------------------------------------


FULL OUTER JOIN – Oracle10g

SELECT ename ,dnameFROM empa e FULL OUTER JOIN dept dON e.deptno = d.deptno;

------------------------------------------------------------| Id | Operation | Name | Rows | Bytes | Cost |------------------------------------------------------------| 0 | SELECT STATEMENT | | 15 | 240 | 13|| 1 | VIEW | | 15 | 240 | 13|| 2 | UNION-ALL | | | | ||* 3 | HASH JOIN OUTER | | 14 | 308 | 7|| 4 | TABLE ACCESS FULL| EMPA | 14 | 126 | 3|| 5 | TABLE ACCESS FULL| DEPT | 4 | 52 | 3||* 6 | HASH JOIN ANTI | | 1 | 16 | 7|| 7 | TABLE ACCESS FULL| DEPT | 4 | 52 | 3|| 8 | TABLE ACCESS FULL| EMPA | 14 | 42 | 3|------------------------------------------------------------

ALTER SESSION SET optimizer_features_enable = '10.2.0.1';


FULL OUTER JOIN – Oracle10g (continued)

Statement is transformed to a UNION construct

― Generates same execution plan as for 10g FULL OUTER JOIN

Native full outer join available in 10.2.0.3 and 10.2.0.4 with a hint

/*+NATIVE_FULL_OUTER_JOIN */ Undocumented parameter

_optimizer_native_full_outer_join

SELECT ename ,dnameFROM empa e ,dept dWHERE e.deptno = d.deptno(+)UNION ALLSELECT null ,dnameFROM dept d2 WHERE NOT EXISTS (SELECT 'x' FROM empa e2 WHERE e2.deptno = d2.deptno);




Two-way Outer Joins



Hash Join Trees


Lateral Joins

Nested Loops Joins

Join Elimination


Two-way Outer Joins

project table linked to a cut down modified version of emp, called empb― Project number 3 (DESIGN) has no employees

PROJ_ID PNAME START_DATE------- --------- ----------- 1 BPR 01-JUL-2002 2 MIGRATION 12-OCT-2002 3 DESIGN 01-NOV-2002

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO PROJ_ID----- ------ -------- ---- ----------- ---- ---- ------ ------- 7782 CLARK MANAGER 7839 09-JUN-1981 2450 10 1 7788 SCOTT ANALYST 7566 19-APR-1987 3000 20 2 7844 TURNER SALESMAN 7698 08-SEP-1981 1500 0 30 1 7499 ALLEN SAlESMAN 7698 20-FEB-1981 1600 300 30 1


DEPTNO DNAME LOC------- ---------- -------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON

deptproj

empb

Two-way Outer Joins

Show details of employees with their projects and departments— Include projects with no employees and departments with no employees

project empb dept

(+) (+)


ANSI Two-way Outer Joins – Expected result

ENAME HIREDATE DEPTNO DNAME PROJ_ID PNAME---------- ----------- ------ ----------- ------- ---------ALLEN 20-FEB-1981 30 SALES 1 BPRTURNER 08-SEP-1981 30 SALES 1 BPRCLARK 09-JUN-1981 10 ACCOUNTING 1 BPRSCOTT 19-APR-1987 20 RESEARCH 2 MIGRATION 40 OPERATIONS 3 DESIGN

Two-way outer joins are allowed but the result may not be as expected

Outer join of empb to both dept and project based on deptno and proj_id values (as requested on the previous slide) should give the following result


ANSI Two-way Outer Joins – Missing Rows

Unexpected results?

SELECT ename, hiredate,d.deptno,dname,p.proj_id,pnameFROM dept d LEFT OUTER JOIN empb e ON e.deptno = d.deptnoRIGHT OUTER JOIN proj pON e.proj_id = p.proj_id;

ENAME HIREDATE DEPTNO DNAME PROJ_ID PNAME---------- ----------- ------ ----------- ------- ---------CLARK 09-JUN-1981 10 ACCOUNTING 1 BPR SCOTT 19-APR-1987 20 RESEARCH 2 MIGRATIONALLEN 20-FEB-1981 30 SALES 1 BPRTURNER 08-SEP-1981 30 SALES 1 BPR 3 DESIGN


ANSI Two-way Outer Joins – Missing Rows (continued)

Reordering the joins still gives another different unexpected result?― Outer joins are not 'symmetrical'

SELECT ename, hiredate,d.deptno,dname,p.proj_id,pnameFROM proj p LEFT OUTER JOIN empb e ON e.proj_id = p.proj_idRIGHT OUTER JOIN dept dON e.deptno = d.deptno;

ENAME HIREDATE DEPTNO DNAME PROJ_ID PNAME---------- ----------- ------ ----------- ------- ---------CLARK 09-JUN-1981 10 ACCOUNTING 1 BPR SCOTT 19-APR-1987 20 RESEARCH 2 MIGRATIONTURNER 08-SEP-1981 30 SALES 1 BPR ALLEN 20-FEB-1981 30 SALES 1 BPR 40 OPERATIONS


ANSI Two-way Outer Joins - Explanation

Explanation of unexpected behaviour— Examine the result of the first join in the first example— The fifth row does not have a value in the proj_id column— This row can not take part in the final join with the proj table

SELECT ename, hiredate,d.deptno,dname,proj_idFROM dept d LEFT OUTER JOIN empb e ON e.deptno = d.deptno;

ENAME HIREDATE DEPTNO DNAME PROJ_ID---------- ----------- ------ ----------- -------CLARK 09-JUN-1981 10 ACCOUNTING 1 SCOTT 19-APR-1987 20 RESEARCH 2TURNER 08-SEP-1981 30 SALES 1 ALLEN 20-FEB-1981 30 SALES 1 40 OPERATIONS


ANSI Two-way Outer Joins – use of FULL

ENAME HIREDATE DEPTNO DNAME PROJ_ID PNAME---------- ----------- ------ ----------- ------- ---------ALLEN 20-FEB-1981 30 SALES 1 BPRTURNER 08-SEP-1981 30 SALES 1 BPRCLARK 09-JUN-1981 10 ACCOUNTING 1 BPRSCOTT 19-APR-1987 20 RESEARCH 2 MIGRATION 40 OPERATIONS 3 DESIGN

SELECT ename,hiredate,d.deptno,dname,p.proj_id,pnameFROM dept d LEFT OUTER JOIN empb e ON e.deptno = d.deptnoFULL OUTER JOIN proj pON e.proj_id = p.proj_id;

Outer joining dept to empb gives a row with NULL in proj_id― This row can not take part in the second outer join

― The second join needs to be a FULL OUTER JOIN


Two-way Outer Joins – Oracle Style

In 11g, Oracle syntax cannot outer join a table to more than one other table

ORA-01417: a table may be outer joined to at most one other table

SELECT ename,hiredate,d.deptno,dname,p.proj_id,pnameFROM dept d, empb e, proj pWHERE e.deptno(+) = d.deptnoAND e.proj_id(+) = p.proj_id;


Two-way Outer Joins – Oracle Style (continued)

But in Oracle12c, this would be the output― Cannot be imitated using ANSI syntax

ENAME HIREDATE DEPTNO DNAME PROJ_ID PNAME---------- ----------- ------ ----------- ------- ----------SCOTT 19-APR-1987 20 RESEARCH 2 MIGRATION ALLEN 20-FEB-1981 30 SALES 1 BPRTURNER 08-SEP-1981 30 SALES 1 BPRCLARK 09-JUN-1981 10 ACCOUNTING 1 BPR 40 OPERATIONS 1 BPR 40 OPERATIONS 2 MIGRATION 40 OPERATIONS 3 DESIGN 30 SALES 2 MIGRATION 30 SALES 3 DESIGN 20 RESEARCH 1 BPR 20 RESEARCH 3 DESIGN 10 ACCOUNTING 2 MIGRATION 10 ACCOUNTING 3 DESIGN


Oracle Outer Joins with Subqueries

ORA-01799: a column may not be outer-joined to a subquery

SELECT ename, hiredate,d.deptno,dnameFROM dept d, empa eWHERE e.deptno(+) = d.deptnoAND e.hiredate(+) = (SELECT MIN(e.hiredate) FROM empa e WHERE e.deptno = d.deptno);

Show each department with its longest serving employee

— Subqueries are not allowed in combination with an outer join condition

What about ANSI joins?


SELECT ename, hiredate,d.deptno,dnameFROM dept d LEFT OUTER JOIN emp eON e.deptno = d.deptnoAND e.hiredate = (SELECT MIN(e.hiredate) FROM emp e WHERE e.deptno = d.deptno);



Two-way Outer Joins



Hash Join Trees


Lateral Joins

Nested Loops Joins

Join Elimination



Oracle uses the ON clause for join conditions

Conditions specified in a WHERE clause are treated as filter conditions

Filter conditions can also be specified in the ON (or USING) clause

Join operations and conditions are effectively processed before the WHERE clause conditions


Oracle Join and Filter Conditions

SELECT dept.deptno,dname,ename,jobFROM dept, empaWHERE empa.deptno(+) = dept.deptnoAND empa.job(+) = 'SALESMAN';

DEPTNO DNAME ENAME JOB------ ----------- -------- -------- 10 ACCOUNTING 20 RESEARCH 30 SALES TURNER SALESMAN 30 SALES ALLEN SALESMAN 40 OPERATIONS

SELECT dept.deptno,dname,ename,jobFROM dept, empaWHERE empa.deptno(+) = dept.deptnoAND empa.job = 'SALESMAN';

DEPTNO DNAME ENAME JOB------ ----------- -------- -------- 30 SALES TURNER SALESMAN 30 SALES ALLEN SALESMAN

Filter applied after the join

Filter applied during the join— Somewhat awkward syntax


ANSI Join and Filter Conditions

SELECT dept.deptno,dname,ename,jobFROM dept LEFT OUTER JOIN empaON empa.deptno = dept.deptnoAND empa.job = 'SALESMAN';

DEPTNO DNAME ENAME JOB------ ----------- ------- -------- 30 SALES TURNER SALESMAN 30 SALES ALLEN SALESMAN 40 OPERATIONS 20 RESEARCH 10 ACCOUNTING

SELECT dept.deptno,dname,ename,jobFROM dept LEFT OUTER JOIN empaON empa.deptno = dept.deptnoWHERE empa.job = 'SALESMAN‘;

DEPTNO DNAME ENAME JOB------ ---------- -------- -------- 30 SALES ALLEN SALESMAN 30 SALES TURNER SALESMAN

Filter applied after the join— Easier to understand due to separation of join conditions from filter conditions

Filter applied during the join

Note the three outer joined rows- one row for each department having no salesmen


Oracle Outer Joins and OR

Oracle syntax cannot cope

SELECT dname ,ename ,job ,loc ,salFROM emp e ,dept dWHERE e.deptno(+) = d.deptnoAND (sal(+) < 1000 OR loc(+) = 'DALLAS')ORDER BY dname;


AND (sal(+) < 1000 OR loc(+) = 'DALLAS') *ERROR :ORA-01719:outer join operator (+) not allowed in operand of OR or IN

ANSI Outer Joins and OR

ANSI join handles OR with outer join

SELECT dname ,ename ,job ,loc ,salFROM emp e RIGHT OUTER JOIN dept dON e.deptno = d.deptnoAND (sal < 1000 OR loc = 'DALLAS')ORDER BY dname;

DNAME ENAME JOB LOC SAL-------------- ---------- --------- ------------- ----ACCOUNTING NEW YORKOPERATIONS BOSTONRESEARCH ADAMS CLERK DALLAS 1100RESEARCH FORD ANALYST DALLAS 3000RESEARCH JONES MANAGER DALLAS 2975RESEARCH SMITH CLERK DALLAS 800RESEARCH SCOTT ANALYST DALLAS 3000SALES JAMES CLERK CHICAGO 950




Two-way Outer Joins



Hash Join Trees


Lateral Joins

Nested Loops Joins

Join Elimination


'Chaining on' the Outer Join

course attendance student

All courses have attendances, all attendances have offerings― Hence outer join is never necessary when joining offering and attendance

Some students do not have attendances

Query :

Show ALL students along with their courses


Data in the Sample Tables

COURSE_ID START_DATE--------- ---------- 1001 14-DEC-11 1002 12-JUL-12 1003 20-NOV-12

COURSE_ID STUDENT_ID --------- ---------- 1001 1111 1002 2299 1003 2299 1002 6789 1003 1111

STUDENT_ID STUDENT_LNAME---------- ------------- 1111 BROWN 2299 ADAMS 4568 COX 5556 TYLER 6789 ROSE

Two students do not have any attendances

All courses and attendances are related


course

attendance

student

Joining course and attendance

Outer join is completely unnecessary as all rows match

C_COURSE_ID A_COURSE_ID A_STUDENT_ID----------- ----------- ------------ 1001 1001 1111 1002 1002 2299 1003 1003 2299 1002 1002 6789 1003 1003 1111

SELECT c.course_id c_course_id ,a.course_id a_course_id ,a.student_id FROM course c INNER JOIN attendance aON c.course_id = a.course_id;

SELECT o.course_id c_course_id ,a.course_id a_course_id ,a.student_id a_student_id FROM attendance a LEFT OUTER JOIN course cON a.course_id = c.course_id;


Joining attendance and student

Outer join is necessary to include students without attendances

SELECT s.student_id s_student_id ,s.student_lname s_student_lname ,a.student_id a_student_id ,a.course_id a_course_id FROM student s LEFT OUTER JOIN attendance aON s.student_id = a.student_id;

S_STUDENT_ID S_LNAME A_STUDENT_ID A_COURSE_ID------------ ------- ------------ ----------- 1111 BROWN 1111 1001 2299 ADAMS 2299 1002 2299 ADAMS 2299 1003 6789 ROSE 6789 1002 1111 BROWN 1111 1003 4568 COX 5556 TYLER


Join Three Tables - Inner join 'loses' students

Rows are lost by the inner join Oracle is smart enough

not to perform the outer join

SELECT s.student_id s_student_id,s.student_lname s_lname ,a.student_id a_student_id,a.course_id a_course_id ,c.course_id c_course_id,c.start_date FROM student s LEFT OUTER JOIN attendance aON s.student_id = a.student_id INNER JOIN course cON c.course_id = a.course_id;

S_STUDENT_ID S_LNAME A_STUDENT_ID A_COURSE_ID C_COURSE_ID START_DATE------------ ------- ------------ ----------- ----------- ---------- 1111 BROWN 1111 1001 1001 14-DEC-11 2299 ADAMS 2299 1002 1002 12-JUL-12 2299 ADAMS 2299 1003 1003 20-NOV-12 6789 ROSE 6789 1002 1002 12-JUL-12 1111 BROWN 1111 1003 1003 20-NOV-12

-----------------------------------------------| Id | Operation | Name |Rows |-----------------------------------------------| 0| SELECT STATEMENT | | 5||* 1| HASH JOIN | | 5||* 2| HASH JOIN | | 5|| 3| TABLE ACCESS FULL| COURSE | 3|| 4| TABLE ACCESS FULL| ATTENDANCE | 5|| 5| TABLE ACCESS FULL | STUDENT | 5|-----------------------------------------------


Chaining on the OUTER JOINSELECT s.student_id s_student_id,s.student_lname s_lname ,a.student_id a_student_id,a.course_id a_course_id ,c.course_id c_course_id,c.start_date FROM student s LEFT OUTER JOIN attendance aON s.student_id = a.student_id LEFT OUTER JOIN course cON c.course_id = a.course_id;

S_STUDENT_ID S_LNAME A_STUDENT_ID A_COURSE_ID C_COURSE_ID START_DATE------------ ------- ------------ ----------- ----------- ---------- 1111 BROWN 1111 1001 1001 14-DEC-11 2299 ADAMS 2299 1002 1002 12-JUL-12 2299 ADAMS 2299 1003 1003 20-NOV-12 6789 ROSE 6789 1002 1002 12-JUL-12 1111 BROWN 1111 1003 1003 20-NOV-12 4568 COX 5556 TYLER

-----------------------------------------------| Id | Operation | Name |Rows |-----------------------------------------------| 0| SELECT STATEMENT | | 5||* 1| HASH JOIN OUTER | | 5||* 2| HASH JOIN OUTER | | 5|| 3| TABLE ACCESS FULL| STUDENT | 5|| 4| TABLE ACCESS FULL| ATTENDANCE | 5|| 5| TABLE ACCESS FULL | COURSE | 3|-----------------------------------------------

Outer join performed between attendance and course when not strictly necessary


Avoiding the second OUTER JOIN

Inner join performed first

Outer join preserves all student rows

SELECT s.student_id s_student_id,s.student_lname s_lname ,a.student_id a_student_id,a.course_id a_course_id ,c.course_id c_course_id,c.start_dateFROM course c JOIN attendance aON c.course_id = a.course_id RIGHT OUTER JOIN student sON s.student_id = a.student_id;

S_STUDENT_ID S_LNAME A_STUDENT_ID A_COURSE_ID C_COURSE_ID START_DATE------------ ------- ------------ ----------- ----------- ---------- 1111 BROWN 1111 1001 1001 14-DEC-11 2299 ADAMS 2299 1002 1002 12-JUL-12 2299 ADAMS 2299 1003 1003 20-NOV-12 6789 ROSE 6789 1002 1002 12-JUL-12 1111 BROWN 1111 1003 1003 20-NOV-12 4568 COX 5556 TYLER

------------------------------------------------| Id | Operation | Name |Rows |------------------------------------------------| 0| SELECT STATEMENT | | 5||* 1| HASH JOIN OUTER | | 5|| 2| TABLE ACCESS FULL | STUDENT | 5|| 3| VIEW | | 5||* 4| HASH JOIN | | 5|| 5| TABLE ACCESS FULL| COURSE | 3|| 6| TABLE ACCESS FULL| ATTENDANCE | 5|------------------------------------------------


Ordering the joins 'Right'

SELECT s.student_id s_student_id,s.student_lname s_lname ,a.student_id a_student_id,a.course_id a_course_id ,c.course_id c_course_id,c.start_date FROM attendance a RIGHT OUTER JOIN student sON s.student_id = a.student_id JOIN course cON c.course_id = a.course_id;

S_STUDENT_ID S_LNAME A_STUDENT_ID A_COURSE_ID C_COURSE_ID START_DATE------------ ------- ------------ ----------- ----------- ---------- 1111 BROWN 1111 1001 1001 14-DEC-11 2299 ADAMS 2299 1002 1002 12-JUL-12 2299 ADAMS 2299 1003 1003 20-NOV-12 6789 ROSE 6789 1002 1002 12-JUL-12 1111 BROWN 1111 1003 1003 20-NOV-12

-----------------------------------------------| Id | Operation | Name |Rows |-----------------------------------------------| 0| SELECT STATEMENT | | 5||* 1 HASH JOIN | | 5||* 2| HASH JOIN | | 5|| 3| TABLE ACCESS FULL| COURSE | 3|| 4| TABLE ACCESS FULL| ATTENDANCE | 5|| 5| TABLE ACCESS FULL | STUDENT | 5|-----------------------------------------------

Right join would be performed first?

Inner join would then lose the outer joined student rows

No outer joins performed




Two-way Outer Joins



Hash Join Trees


Lateral Joins

Nested Loops Joins

Join Elimination


Processing a Hash Join

NAME CITY ...

SCOTT BATH ...

PAYNE YORK ...

FOX LEEDS ...

SMITH ELY ...

WOOD BATH ...

ADAMS LONDON ...

ADAMS LONDON ...

FOX LEEDS ...

PAYNE YORK ...

SCOTT BATH ...

WOOD BATH ...

SMITH ELY ...

ORD_ID NAME ...

1 SMITH ...

2 PAYNE ...

3 FOX ...

4 SCOTT ...

5 WOOD ...

6 ADAMS ...

Hash table

Build Table (customers)

Probe Table (orders)


Join Trees for T1 T2 T3 T4

T2T1

T3

T4

Left deep tree

Output of T1 join T2 probed by T3

Output of T1 join T2 join T3 probed by T4

Hash table built on T1 probed by T2

T2 T1

T3

T4

Right deep tree

Hash table built on T3probed by result of T1 join T2

Hash table built on T2probed by T1

Hash table built on T4probed by result of T1 join T2 join T3


Bushy tree

T2T1 T3 T4 T2T1

T3

T4

Zig-zag tree


Join Trees for T1 T2 T3 T4 (continued)

Summary of Hash Join Trees

Left-deep

― Result sets are formed before build of next hash table

― Workarea discarded after each subsequent join

― Only one workarea used

Right-deep― Hash tables on T3 and T4 can be built 'in parallel' with hash table on T1

― Three workareas can be used

― Could be useful when the results of joins are larger than the two sets of rows being joined


Tree Combinations

Tables Left-Deep Trees Bushy Trees(inc. Left and Right)

1 1 1

2 2 2

3 6 12

4 24 120

5 120 1,680

6 720 30,240

Optimizer normally considers only left-deep trees― Left deep joins cover most requirements― Number of left-deep trees = n!― Total number of join trees = (2n-2)!/(n-1)!

Can Oracle be forced to perform a bushy tree?


Four Table Join Scenario

pt

PT_ID PT_NAME----- ------- 1 ptname1 2 ptname2 3 ptname3 : :

wa

WA_ID WA_NAME----- ------- 1 name1 2 name2 3 name3 : :

p

P_ID P_NAME WA_ID PT_ID---- ------ ----- ----- 1 pname1 1 1 2 pname2 2 2 3 pname3 3 3 : : : :

sa

ID NAME WA_ID-- ---- ----- 1 x 1 2 y 2 3 z 3 : : :


Right Deep Join Tree

Oracle uses hints internally to force a right deep join in this case

SELECT /*+GATHER_PLAN_STATISTICS */ name FROM sa JOIN wa ON wa.wa_id = sa.wa_id JOIN p ON wa.wa_id = p.wa_id JOIN pt ON pt.pt_id = p.pt_id;

-----------------------------| SELECT STATEMENT | || HASH JOIN | || TABLE ACCESS FULL | SA || HASH JOIN | || TABLE ACCESS FULL | WA || HASH JOIN | || TABLE ACCESS FULL| PT || TABLE ACCESS FULL| P |-----------------------------

SWAP_JOIN_INPUTS(@"SEL$EE94F965" "PT"@"SEL$3")SWAP_JOIN_INPUTS(@"SEL$EE94F965" "WA"@"SEL$1")SWAP_JOIN_INPUTS(@"SEL$EE94F965" "SA"@"SEL$1")

Internally generated hints


Left Deep Join Tree

Left deep tree can be forced using hints

-----------------------------| SELECT STATEMENT | || HASH JOIN | || HASH JOIN | || HASH JOIN | || TABLE ACCESS FULL| PT || TABLE ACCESS FULL| P || TABLE ACCESS FULL | WA || TABLE ACCESS FULL | SA |-----------------------------

SELECT /*+GATHER_PLAN_STATISTICS no_swap_join_inputs(wa) no_swap_join_inputs(p) no_swap_join_inputs(pt) no_swap_join_inputs(sa)*/ name FROM sa JOIN wa ON wa.wa_id = sa.wa_id JOIN p ON wa.wa_id = p.wa_id JOIN pt ON pt.pt_id = p.pt_id;


Forcing a Bushy Tree

In complex decision support scenarios a bushy tree can be a good plan

― Cannot be forced using '(', ')' or ORDERED, LEADING or other 'conventional' hints

― Must use inline views and a selection of less well known hints to stop Oracle merging the views internally

SELECT /*+no_merge(v1) no_merge(v2)*/ nameFROM (SELECT sa.name ,wa.wa_id FROM sa JOIN wa ON wa.wa_id = sa.wa_id) v1 JOIN (SELECT p.wa_id FROM p JOIN pt ON pt.pT_id = p.pT_id) v2ON v1.wa_id = v2.wa_id;

-----------------------------| SELECT STATEMENT | || HASH JOIN | || VIEW | || HASH JOIN | || TABLE ACCESS FULL| PT || TABLE ACCESS FULL| P || VIEW | || HASH JOIN | || TABLE ACCESS FULL| WA || TABLE ACCESS FULL| SA |-----------------------------




Two-way Outer Joins



Hash Join Trees


Lateral Joins

Nested Loops Joins

Join Elimination


Hash Join Plans

Semi-joins

― Often occur with EXISTS and IN subqueries

― Used when existence tests are required

Find departments which have employees

― Semi-join returns a department only once no matter how many employees work for it

SELECT * FROM deptWHERE EXISTS (SELECT 'x' FROM emp WHERE deptno = dept.deptno);


Right Semi Join

From Oracle 10g, the driving table can be automatically switched

― Can depend on size of input rowsets

― SWAP_JOIN_INPUTS hint is used internally

• Often used to avoid high memory usage (monitor OMEM with dbms_xplan)

-------------------------------------|Operation |Name |Rows |-------------------------------------|SELECT STATEMENT | |8192 || HASH JOIN RIGHT SEMI| |8192 || VIEW |VW_SQ_1|7168 || TABLE ACCESS FULL |EMP |7168 || TABLE ACCESS FULL |DEPT |8192 |-------------------------------------

-----------------------------------|Operation |Name |Rows|-----------------------------------|SELECT STATEMENT | | 4|| HASH JOIN SEMI | | 4|| TABLE ACCESS FULL |DEPT | 4|| VIEW |VW_SQ_1|7168|| TABLE ACCESS FULL|EMP |7168|-----------------------------------

dept : 8192 rows

emp : 7168 rows

dept : 4 rows

emp : 7168 rows


Departments with no Employees

SELECT * FROM deptWHERE deptno NOT IN (SELECT deptno FROM emp);

DEPTNO DNAME LOC------ ---------- ------ 40 OPERATIONS BOSTON

SELECT * FROM dept xWHERE NOT EXISTS (SELECT 1 FROM emp y WHERE y.deptno = x.deptno);


No Index and no NOT NULL Constraint on emp.deptno

Oracle Version

NOT IN plan NOT EXISTS plan

8i SELECT STATEMENT FILTER TABLE ACCESS FULL DEPT TABLE ACCESS FULL EMP

SELECT STATEMENT FILTER TABLE ACCESS FULL DEPT TABLE ACCESS FULL EMP


SELECT STATEMENT HASH JOIN ANTI TABLE ACCESS FULL DEPT TABLE ACCESS FULL EMP

10g SELECT STATEMENT FILTER TABLE ACCESS FULL DEPT TABLE ACCESS FULL EMP


11g SELECT STATEMENT HASH JOIN ANTI NA TABLE ACCESS FULL DEPT TABLE ACCESS FULL EMP



NOT NULL constraint on emp.deptno

Oracle Version



SELECT STATEMENT FILTER TABLE ACCESS FULL DEPT TABLE ACCESS FULL EMP





11g SELECT STATEMENT HASH JOIN ANTI SNA TABLE ACCESS FULL DEPT TABLE ACCESS FULL EMP



Index on emp.deptno, no NOT NULL constraint

Oracle Version



SELECT STATEMENT FILTER TABLE ACCESS FULL DEPT INDEX RANGE SCAN EMP$DEPTNO




SELECT STATEMENT NESTED LOOPS ANTI TABLE ACCESS FULL DEPT INDEX RANGE SCAN EMP$DEPTNO

11g SELECT STATEMENT HASH JOIN ANTI NA TABLE ACCESS FULL DEPT TABLE ACCESS FULL EMP

SELECT STATEMENT HASH JOIN ANTI TABLE ACCESS FULL DEPT INDEX FAST FULL SCAN EMP$DEPTNO 58Carl Dudley – University of Wolverhampton

Index and NOT NULL Constraint on emp.deptno

Version NOT IN plan NOT EXISTS plan

8i SELECT STATEMENT FILTER TABLE ACCESS FULL DEPT INDEX RANGE SCAN EMP$DEPTNO


9i SELECT STATEMENT FILTER TABLE ACCESS FULL DEPT INDEX FULL SCAN EMP$DEPTNO


10g SELECT STATEMENT FILTER TABLE ACCESS FULL DEPT INDEX FULL SCAN EMP$DEPTNO


11g SELECT STATEMENT HASH JOIN ANTI SNA TABLE ACCESS FULL DEPT INDEX FULL SCAN EMP$DEPTNO


If the column on the right hand side of the condition (emp.deptno) has no NOT NULL constraint, then NA is used — If it is declared NOT NULL, SNA is used, along with an available index




Two-way Outer Joins



Hash Join Trees


Lateral Joins

Nested Loops Joins

Join Elimination


Lateral Joins

Inline views cannot reference columns outside of the view

― Considered to be out of scope

SELECT dname ,enameFROM dept d ,(SELECT ename FROM emp e WHERE e.deptno = d.deptno);

WHERE e.deptno = d.deptno) *ERROR : ORA-00904: "D"."DEPTNO": invalid identifier


Lateral views allow such references

― Used internally

Similar to correlated subqueries

Lateral Joins in Oracle12c

Need to set an event on Oracle11g

― LATERAL keyword can then be used to allow correlation

SELECT dname ,enameFROM dept d ,LATERAL(SELECT ename FROM emp e WHERE e.deptno = d.deptno);

DNAME ENAME-------------- ----------RESEARCH SMITHSALES ALLENSALES WARD : :

ALTER SESSION SET EVENTS '22829 TRACE NAME CONTEXT FOREVER';

Identical execution plan to

equivalent equi-join


Lateral Outer Join Syntax

SELECT dname ,ename ,job ,loc ,salFROM dept ,LATERAL(SELECT ename,job,sal FROM emp WHERE emp.deptno = dept.deptno AND (sal < 1000 OR job = 'ANALYST'))(+);

DNAME ENAME JOB LOC SAL-------------- ---------- --------- ------------- ----------ACCOUNTING NEW YORKRESEARCH SMITH CLERK DALLAS 800RESEARCH SCOTT ANALYST DALLAS 3000RESEARCH FORD ANALYST DALLAS 3000SALES JAMES CLERK CHICAGO 950OPERATIONS BOSTON


CROSS APPLY and OUTER APPLY

Compatibility issues with SQL Server migration tools


SELECT dname,ename,job,loc,salFROM dept CROSS APPLY (SELECT ename,job,sal FROM emp WHERE emp.deptno = dept.deptno AND (sal < 1000 OR job = 'ANALYST'))

SELECT dname,ename,job,loc,salFROM dept OUTER APPLY (SELECT ename,job,sal FROM emp WHERE emp.deptno = dept.deptno AND (sal < 1000 OR job = 'ANALYST'))

Equivalent Outer Join Plans

-------------------------------------------| Id | Operation | Name | Rows |-------------------------------------------| 0 | SELECT STATEMENT | | 5 ||* 1 | HASH JOIN OUTER | | 5 || 2 | TABLE ACCESS FULL| DEPT | 4 ||* 3 | TABLE ACCESS FULL| EMP | 4 |-------------------------------------------


SELECT dname,ename,job,loc,salFROM dept OUTER APPLY (SELECT ename,job,sal FROM emp WHERE emp.deptno = dept.deptno AND (sal < 1000 OR job = 'ANALYST'))

SELECT dname,ename,job,loc,salFROM dept ,LATERAL(SELECT ename,job,sal FROM emp WHERE emp.deptno = dept.deptno AND (sal < 1000 OR job = 'ANALYST'))(+);

SELECT dname,ename,job,loc,salFROM dept, empWHERE emp.deptno(+) = dept.deptnoAND (sal(+) < 1000 OR job(+) = 'ANALYST')

Use of CROSS/OUTER APPLY

When join sets are not known in advance Example purely for illustration :

Number of emp rows to join is governed by highest salary in that department

― Note use of subquery in FETCH clause

• Can use any appropriate variable or expression


SELECT deptno ,empno ,ename ,salFROM dept OUTER APPLY (SELECT empno ,ename ,sal FROM emp WHERE emp.deptno = dept.deptno order by sal desc FETCH FIRST (SELECT MAX(sal)/1500 FROM emp WHERE emp.deptno = dept.deptno) ROWS ONLY)ORDER BY dept.deptno;

CROSS/OUTER APPLY with Table level functions


CREATE TYPE emp_row_type as OBJECT ( empno VARCHA2R(8), ename VARCHAR2(20), deptno VARCHAR2(20));

CREATE TYPE emp_table_type as TABLE OF emp_row_type;

CREATE OR REPLACE FUNCTION get_all_emps(pi_deptno in number) RETURN emp_table_type PIPELINED ASBEGIN FOR cur IN (SELECT * FROM emp where deptno = pi_deptno) LOOP PIPE ROW(emp_row_type(cur.empno,cur.ename,cur.deptno)); END LOOP; RETURN; END;

Table Function Joins


DEPTNO DNAME LOC EMPNO ENAME DEPTNO------ -------------- ------------- -------- -------------------- ------ 10 ACCOUNTING NEW YORK 7782 CLARK 10 : : : : : : 20 RESEARCH DALLAS 7369 SMITH 20 : : : : : : 30 SALES CHICAGO 7900 JAMES 30 : : : : : : 40 OPERATIONS BOSTON

SELECT * FROM dept, TABLE(get_all_emps(dept.deptno));

SELECT * FROM dept CROSS APPLY TABLE(get_all_emps(dept.deptno));

SELECT * FROM dept, TABLE(get_all_emps(dept.deptno))(+);

SELECT * FROM dept OUTER APPLY TABLE(get_all_emps(dept.deptno));

DEPTNO DNAME LOC EMPNO ENAME DEPTNO------ -------------- ------------- -------- -------------------- ------ 10 ACCOUNTING NEW YORK 7782 CLARK 10 : : : : : : 20 RESEARCH DALLAS 7369 SMITH 20 : : : : : : 30 SALES CHICAGO 7900 JAMES 30 : : : : : :



Two-way Outer Joins



Hash Join Trees


Lateral Joins

Nested Loops Joins

Join Elimination


Oracle11g Nested Loops Joins

SELECT /*+ LEADING(e) USE_NL(d)*/ *FROM emp e ,dept dWHERE e.deptno = d.deptno AND e.sal = 3000;

------------------------------------------| SELECT STATEMENT | || NESTED LOOPS | || NESTED LOOPS | | TABLE ACCESS FULL | EMP || INDEX UNIQUE SCAN | PK_DEPT || TABLE ACCESS BY INDEX ROWID| DEPT |------------------------------------------

Batch style operation using an index― ROWIDs collected from an index― Used in a second nested loops style operation against the driven table

• Can reduce physical I/O and improve performance in certain cases

• Could reduce readability of execution plans


Reverting to Oracle10g Nested Loops Joins

------------------------------------------| SELECT STATEMENT | || NESTED LOOPS | || TABLE ACCESS FULL | EMP || TABLE ACCESS BY INDEX ROWID| DEPT || INDEX UNIQUE SCAN | PK_DEPT |------------------------------------------

SELECT /*+ LEADING(e) USE_NL(d) NO_NLJ_BATCHING(d)*/ *FROM emp e ,dept dWHERE e.deptno = d.deptno AND e.sal = 3000;ALTER SESSION SET OPTIMIZER_FEATURES_ENABLE = '10.2.0.5';

Use a hint or set a parameter

New undocumented parameter _nlj_batching_enabled (0 or 1)71Carl Dudley – University of Wolverhampton

Other relevant hintsNLJ_BATCHING()NLJ_PREFETCH()NO_NLJ_PREFETCH()



Two-way Outer Joins



Hash Join Trees


Lateral Joins

Nested Loops Joins

Join Elimination


Join Elimination – the Ins and Outs

Some unnecessary joins are eliminated

SELECT e.ename ,e.deptnoFROM emp e ,dept dWHERE e.deptno = d.deptno

------------------------------------------| Id | Operation | Name | Rows |------------------------------------------| 0 | SELECT STATEMENT | | 14 ||* 1 | TABLE ACCESS FULL| EMP | 14 |------------------------------------------Predicate Information (identified by operation id):--------------------------------------------------- 1 - filter("E"."DEPTNO" IS NOT NULL)

SELECT e.ename ,e.deptnoFROM emp e ,dept dWHERE e.deptno = d.deptno(+)

No access to dept table (or any dept table index) in both cases on 11g Filter is unnecessary if deptno has a NOT NULL constraint


Conditions for Join Elimination

Oracle 10g Oracle11g

Inner Join Outer join Inner Join Outer join

No constraints Primary key on dept

(or UK)

Foreign key on deptno in emp


Join Elimination - Antijoins

SELECT e.empno, e.enameFROM emp eWHERE NOT EXISTS (SELECT 1 FROM dept d WHERE d.deptno = e.deptno);

SELECT STATEMENT TABLE ACCESS FULL EMP

filter("E"."DEPTNO" IS NOT NULL)


SELECT STATEMENT NESTED LOOPS ANTI TABLE ACCESS FULL EMP INDEX UNIQUE SCAN PK_DEPT

filter("E"."DEPTNO"="D”.”DEPTNO”

SELECT STATEMENT FILTER TABLE ACCESS FULL EMP

filter(NULL IS NOT NULL)

Foreign key present

No foreign key

Foreign key and NOT NULL

Dummy filter showing NO access to ANY table

Anti joins can also be eliminated

Join Elimination - Semijoins

SELECT e.empno, e.enameFROM emp eWHERE EXISTS (SELECT 1 FROM dept d WHERE d.deptno = e.deptno);

SELECT STATEMENT TABLE ACCESS FULL EMP

filter("E"."DEPTNO" IS NOT NULL)


SELECT STATEMENT NESTED LOOPS SEMI TABLE ACCESS FULL EMP INDEX UNIQUE SCAN PK_DEPT

filter("E"."DEPTNO"="D”.”DEPTNO”

SELECT STATEMENT FILTER TABLE ACCESS FULL EMP

Foreign key present

No foreign key

Foreign key and NOT NULL

No filter is necessary

Outer Join Elimination - Implications

A view used on the system

― Part of an application

― No access made to dept table even though join is embedded in view

• Access is only to the emp table

• Does not eliminate access to emp when referencing columns in dept― Control with hints

ELIMINATE_JOIN NO_ELIMINATE_JOIN― Control with hidden parameter

_optimizer_join_elimination_enabled

CREATE VIEW empdept AS SELECT e.ename ,e.job ,e.deptno ,d.dname ,d.locFROM emp e ,dept dWHERE e.deptno = d.deptno(+);

SELECT ename,job FROM empdept;


Undocumented ParametersKSPPINM KSPPSTVL--------------------------------------------- ---------_lm_node_join_opt FALSE_abort_recovery_on_join FALSE_hash_join_enabled TRUE_multi_join_key_table_lookup TRUE_force_hash_join_spill FALSE_always_anti_join CHOOSE_optimizer_null_aware_antijoin TRUE_convert_set_to_join FALSE_push_join_predicate TRUE_push_join_union_view TRUE_push_join_union_view2 TRUE_optimizer_join_sel_sanity_check TRUE_ordered_semijoin TRUE_always_semi_join CHOOSE_full_pwise_join_enabled TRUE_partial_pwise_join_enabled TRUE_index_join_enabled TRUE_improved_outerjoin_card TRUE_cost_equality_semi_join TRUE_new_initial_join_orders TRUE_oneside_colstat_for_equijoins TRUE_gs_anti_semi_join_allowed TRUE_optim_new_default_join_sel TRUE_optimizer_new_join_card_computation TRUE_optimizer_sortmerge_join_enabled TRUE_optimizer_dim_subq_join_sel TRUE_optimizer_join_order_control 3_optimizer_join_elimination_enabled TRUE_optimizer_sortmerge_join_inequality TRUE_selfjoin_mv_duplicates TRUE_optimizer_aw_join_push_enabled TRUE_optimizer_native_full_outer_join FORCE_optimizer_eliminate_filtering_join TRUE_optimizer_join_factorization TRUE_optimizer_outer_join_to_inner TRUE_optimizer_full_outer_join_to_outer TRUE_xsolapi_sql_all_multi_join_non_base_hints_xsolapi_sql_enable_aw_join TRUE

SELECT ksppinm ,ksppstvl FROM x$ksppi I ,x$ksppcv vWHERE v.indx =i.indx AND ksppinm LIKE '%join%';

Around 2750 undocumented parameters on 11g


Hints from v$sql_hint

NAME SQL_FEATURE CLASS---------------------------- ---------------------------- ------------------------APPEND QKSFM_CBO APPENDNO_MONITORING QKSFM_ALL NO_MONITORINGNO_SQL_TUNE QKSFM_ALL NO_SQL_TUNEIGNORE_WHERE_CLAUSE QKSFM_ALL IGNORE_WHERE_CLAUSENO_QUERY_TRANSFORMATION QKSFM_TRANSFORMATION NO_QUERY_TRANSFORMATIONOPTIMIZER_FEATURES_ENABLE QKSFM_ALL OPTIMIZER_FEATURES_ENABLGATHER_PLAN_STATISTICS QKSFM_GATHER_PLAN_STATISTICS GATHER_PLAN_STATISTICSIGNORE_OPTIM_EMBEDDED_HINTS QKSFM_ALL IGNORE_OPTIM_EMBEDDED_HITABLE_STATS QKSFM_STATS TABLE_STATSRULE QKSFM_RBO MODECHOOSE QKSFM_CHOOSE MODEFIRST_ROWS QKSFM_FIRST_ROWS MODEORDERED QKSFM_CBO ORDEREDORDERED_PREDICATES QKSFM_CBO ORDERED_PREDICATESPUSH_PRED QKSFM_FILTER_PUSH_PRED PUSH_PREDELIMINATE_JOIN QKSFM_TABLE_ELIM ELIMINATE_JOINNO_ELIMINATE_JOIN QKSFM_TABLE_ELIM ELIMINATE_JOINOUTER_JOIN_TO_INNER QKSFM_OUTER_JOIN_TO_INNER OUTER_JOIN_TO_INNERNO_OUTER_JOIN_TO_INNER QKSFM_OUTER_JOIN_TO_INNER OUTER_JOIN_TO_INNERHASH_AJ QKSFM_CBO ANTIJOINNL_AJ QKSFM_CBO ANTIJOINSEMIJOIN QKSFM_TRANSFORMATION SEMIJOINHASH_SJ QKSFM_CBO SEMIJOINNL_SJ QKSFM_CBO SEMIJOINSTAR QKSFM_STAR_TRANS STARSET_TO_JOIN QKSFM_SET_TO_JOIN SET_TO_JOIN

273 hints on 11g




Carl Dudley

University of Wolverhampton, UK

Oracle ACE Director

[email protected]

Carl Dudley – University of Wolverhampton 1 Oracle Join Techniques Carl Dudley University of...

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