[튜닝워크숍] 해시 조인 실행계획 제어

-- EMP, DEPT 생성
CREATE TABLE DEPT
 ( DEPTNO NUMBER(2) CONSTRAINT PK_DEPT PRIMARY KEY,
	 DNAME VARCHAR2(14) ,
	 LOC VARCHAR2(13) ) ;
	
INSERT INTO DEPT VALUES
	(10,'ACCOUNTING','NEW YORK');
	
INSERT INTO DEPT VALUES (20,'RESEARCH','DALLAS');

INSERT INTO DEPT VALUES
	(30,'SALES','CHICAGO');

INSERT INTO DEPT VALUES
	(40,'OPERATIONS','BOSTON');

COMMIT;

CREATE TABLE EMP
( EMPNO NUMBER(4) CONSTRAINT PK_EMP PRIMARY KEY,
	ENAME VARCHAR2(10),
	JOB VARCHAR2(9),
	MGR NUMBER(4),
	HIREDATE DATE,
	SAL NUMBER(7,2),
	COMM NUMBER(7,2),
	DEPTNO NUMBER(2) );
	
INSERT INTO EMP VALUES
(7369,'SMITH','CLERK',7902,to_date('17-12-1980','dd-mm-yyyy'),800,NULL,20);
INSERT INTO EMP VALUES
(7499,'ALLEN','SALESMAN',7698,to_date('20-2-1981','dd-mm-yyyy'),1600,300,30);
INSERT INTO EMP VALUES
(7521,'WARD','SALESMAN',7698,to_date('22-2-1981','dd-mm-yyyy'),1250,500,30);
INSERT INTO EMP VALUES
(7566,'JONES','MANAGER',7839,to_date('2-4-1981','dd-mm-yyyy'),2975,NULL,20);
INSERT INTO EMP VALUES
(7654,'MARTIN','SALESMAN',7698,to_date('28-9-1981','dd-mm-yyyy'),1250,1400,30);
INSERT INTO EMP VALUES
(7698,'BLAKE','MANAGER',7839,to_date('1-5-1981','dd-mm-yyyy'),2850,NULL,30);
INSERT INTO EMP VALUES
(7782,'CLARK','MANAGER',7839,to_date('9-6-1981','dd-mm-yyyy'),2450,NULL,10);
INSERT INTO EMP VALUES
(7788,'SCOTT','ANALYST',7566,to_date('13-7-1987', 'dd-mm-yyyy')-85,3000,NULL,20);
INSERT INTO EMP VALUES
(7839,'KING','PRESIDENT',NULL,to_date('17-11-1981','dd-mm-yyyy'),5000,NULL,10);
INSERT INTO EMP VALUES
(7844,'TURNER','SALESMAN',7698,to_date('8-9-1981','dd-mm-yyyy'),1500,0,30);
INSERT INTO EMP VALUES
(7876,'ADAMS','CLERK',7788,to_date('13-7-1987', 'dd-mm-yyyy')-51,1100,NULL,20);
INSERT INTO EMP VALUES
(7900,'JAMES','CLERK',7698,to_date('3-12-1981','dd-mm-yyyy'),950,NULL,30);
INSERT INTO EMP VALUES
(7902,'FORD','ANALYST',7566,to_date('3-12-1981','dd-mm-yyyy'),3000,NULL,20);
INSERT INTO EMP VALUES
(7934,'MILLER','CLERK',7782,to_date('23-1-1982','dd-mm-yyyy'),1300,NULL,10);

COMMIT;

-- 해시조인실습데이터 생성
create table a
as
select * from scott.dept;

create table b
as
select * from scott.emp;

create table c
as
select * from scott.emp, (select rownum as no from dual connect by level <= 100);


exec dbms_stats.gather_table_stats(user, 'a');
exec dbms_stats.gather_table_stats(user, 'b');
exec dbms_stats.gather_table_stats(user, 'c');

select /*+                  */ * 
from   a, b, c
where  a.deptno = b.deptno
and    b.empno  = c.empno