Oracle PL/SQL Tutorial/Query Select/EXISTS
Содержание
EXISTS and NOT EXISTS Versus IN and NOT IN
- EXISTS is different from IN.
- EXISTS just checks for the existence of rows, whereas IN checks actual values.
- EXISTS typically offers better performance than IN with subqueries.
- You should use EXISTS rather than IN wherever possible.
- When a list of values contains a null, NOT EXISTS returns true, but NOT IN returns false.
<source lang="sql">
SQL> -- create demo table SQL> create table Employee(
2 EMPNO NUMBER(3), 3 ENAME VARCHAR2(15 BYTE), 4 HIREDATE DATE, 5 ORIG_SALARY NUMBER(6), 6 CURR_SALARY NUMBER(6), 7 REGION VARCHAR2(1 BYTE), 8 MANAGER_ID NUMBER(3) 9 ) 10 /
Table created. SQL> SQL> create table job (
2 EMPNO NUMBER(3), 3 jobtitle VARCHAR2(20 BYTE) 4 ) 5 /
Table created. SQL> SQL> insert into job (EMPNO, Jobtitle) values (1,"Tester"); 1 row created. SQL> insert into job (EMPNO, Jobtitle) values (2,"Accountant"); 1 row created. SQL> insert into job (EMPNO, Jobtitle) values (3,"Developer"); 1 row created. SQL> insert into job (EMPNO, Jobtitle) values (4,"COder"); 1 row created. SQL> insert into job (EMPNO, Jobtitle) values (5,"Director"); 1 row created. SQL> insert into job (EMPNO, Jobtitle) values (6,"Mediator"); 1 row created. SQL> insert into job (EMPNO, Jobtitle) values (7,"Proffessor"); 1 row created. SQL> insert into job (EMPNO, Jobtitle) values (8,"Programmer"); 1 row created. SQL> insert into job (EMPNO, Jobtitle) values (9,"Developer"); 1 row created. SQL> SQL> SQL> -- prepare data SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (1, "Jason", to_date("19960725","YYYYMMDD"), 1234, 8767, "E", 2)
3 /
1 row created. SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (2, "John", to_date("19970715","YYYYMMDD"), 2341, 3456, "W", 3)
3 /
1 row created. SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (3, "Joe", to_date("19860125","YYYYMMDD"), 4321, 5654, "E", 3)
3 /
1 row created. SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (4, "Tom", to_date("20060913","YYYYMMDD"), 2413, 6787, "W", 4)
3 /
1 row created. SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (5, "Jane", to_date("20050417","YYYYMMDD"), 7654, 4345, "E", 4)
3 /
1 row created. SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (6, "James", to_date("20040718","YYYYMMDD"), 5679, 6546, "W", 5)
3 /
1 row created. SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION, MANAGER_ID)
2 values (7, "Jodd", to_date("20030720","YYYYMMDD"), 5438, 7658, "E", 6)
3 /
1 row created. SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION)
2 values (8, "Joke", to_date("20020101","YYYYMMDD"), 8765, 4543, "W")
3 /
1 row created. SQL> insert into Employee(EMPNO, EName, HIREDATE, ORIG_SALARY, CURR_SALARY, REGION)
2 values (9, "Jack", to_date("20010829","YYYYMMDD"), 7896, 1232, "E")
3 /
1 row created. SQL> SQL> SQL> SQL> -- display data in the table SQL> select * from Employee
2 /
EMPNO ENAME HIREDATE ORIG_SALARY CURR_SALARY R MANAGER_ID
--------------- --------- ----------- ----------- - ----------
1 Jason 25-JUL-96 1234 8767 E 2
2 John 15-JUL-97 2341 3456 W 3
3 Joe 25-JAN-86 4321 5654 E 3
4 Tom 13-SEP-06 2413 6787 W 4
5 Jane 17-APR-05 7654 4345 E 4
6 James 18-JUL-04 5679 6546 W 5
7 Jodd 20-JUL-03 5438 7658 E 6
8 Joke 01-JAN-02 8765 4543 W
9 Jack 29-AUG-01 7896 1232 E
9 rows selected. SQL> select * from job
2 /
EMPNO JOBTITLE
--------------------
1 Tester
2 Accountant
3 Developer
4 COder
5 Director
6 Mediator
7 Proffessor
8 Programmer
9 Developer
9 rows selected. SQL> SQL> SELECT empno, ename
2 FROM employee 3 WHERE NOT EXISTS (null);
WHERE NOT EXISTS (null)
*
ERROR at line 3: ORA-00928: missing SELECT keyword
SQL> SQL> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL> drop table job
2 /
Table dropped.</source>
exists in subquery
<source lang="sql">
SQL> SQL> create table emp
2 ( empno NUMBER(4) constraint E_PK primary key 3 , ename VARCHAR2(8) 4 , init VARCHAR2(5) 5 , job VARCHAR2(8) 6 , mgr NUMBER(4) 7 , bdate DATE 8 , sal NUMBER(6,2) 9 , comm NUMBER(6,2) 10 , deptno NUMBER(2) default 10 11 ) ;
Table created. SQL> insert into emp values(1,"Tom","N", "TRAINER", 13,date "1965-12-17", 800 , NULL, 20); 1 row created. SQL> insert into emp values(2,"Jack","JAM", "Tester",6,date "1961-02-20", 1600, 300, 30); 1 row created. SQL> insert into emp values(3,"Wil","TF" , "Tester",6,date "1962-02-22", 1250, 500, 30); 1 row created. SQL> insert into emp values(4,"Jane","JM", "Designer", 9,date "1967-04-02", 2975, NULL, 20); 1 row created. SQL> insert into emp values(5,"Mary","P", "Tester",6,date "1956-09-28", 1250, 1400, 30); 1 row created. SQL> insert into emp values(6,"Black","R", "Designer", 9,date "1963-11-01", 2850, NULL, 30); 1 row created. SQL> insert into emp values(7,"Chris","AB", "Designer", 9,date "1965-06-09", 2450, NULL, 10); 1 row created. SQL> insert into emp values(8,"Smart","SCJ", "TRAINER", 4,date "1959-11-26", 3000, NULL, 20); 1 row created. SQL> insert into emp values(9,"Peter","CC", "Designer",NULL,date "1952-11-17", 5000, NULL, 10); 1 row created. SQL> insert into emp values(10,"Take","JJ", "Tester",6,date "1968-09-28", 1500, 0, 30); 1 row created. SQL> insert into emp values(11,"Ana","AA", "TRAINER", 8,date "1966-12-30", 1100, NULL, 20); 1 row created. SQL> insert into emp values(12,"Jane","R", "Manager", 6,date "1969-12-03", 800 , NULL, 30); 1 row created. SQL> insert into emp values(13,"Fake","MG", "TRAINER", 4,date "1959-02-13", 3000, NULL, 20); 1 row created. SQL> insert into emp values(14,"Mike","TJA","Manager", 7,date "1962-01-23", 1300, NULL, 10); 1 row created. SQL> create table offerings
2 ( course VARCHAR2(6) 3 , begindate DATE 4 , trainer NUMBER(4) 5 , location VARCHAR2(8) 6 ) ;
Table created. SQL> insert into offerings values ("SQL",date "2009-04-12",13,"DALLAS" ); 1 row created. SQL> insert into offerings values ("OAU",date "2009-08-10",4,"CHICAGO"); 1 row created. SQL> insert into offerings values ("SQL",date "2009-10-04",1,"SEATTLE"); 1 row created. SQL> insert into offerings values ("SQL",date "2009-12-13",1,"DALLAS" ); 1 row created. SQL> insert into offerings values ("JAV",date "2009-12-13",4,"SEATTLE"); 1 row created. SQL> insert into offerings values ("XML",date "2000-02-03",1,"DALLAS" ); 1 row created. SQL> insert into offerings values ("JAV",date "2000-02-01",11,"DALLAS" ); 1 row created. SQL> insert into offerings values ("PLS",date "2000-09-11",8,"DALLAS" ); 1 row created. SQL> insert into offerings values ("XML",date "2000-09-18",NULL,"SEATTLE"); 1 row created. SQL> insert into offerings values ("OAU",date "2000-09-27",13,"DALLAS" ); 1 row created. SQL> insert into offerings values ("ERM",date "2001-01-15",NULL, NULL ); 1 row created. SQL> insert into offerings values ("PRO",date "2001-02-19",NULL,"DALLAS" ); 1 row created. SQL> insert into offerings values ("RSD",date "2001-02-24",8,"CHICAGO"); 1 row created. SQL> SQL> select e.*
2 from emp e
3 where exists (select o.*
4 from offerings o
5 where o.course = "SQL"
6 and o.trainer = e.empno);
EMPNO ENAME INIT JOB MGR BDATE SAL COMM
-------- ----- -------- ---------- ---------- ---------- ----------
DEPTNO
1 Tom N TRAINER 13 17-12-1965 800
20
13 Fake MG 4 13-02-1959 3000
20
SQL> drop table offerings; Table dropped. SQL> drop table emp; Table dropped. SQL></source>
Exist with subquery
<source lang="sql">
SQL> SQL> create table course_schedule
2 ( course VARCHAR2(6) 3 , begindate DATE 4 , trainer NUMBER(4) 5 , location VARCHAR2(20)) ;
Table created. SQL> SQL> SQL> insert into course_schedule values ("SQL",date "1999-04-12",1,"VANCOUVER" ); 1 row created. SQL> insert into course_schedule values ("OAU",date "1999-08-10",2,"CHICAGO"); 1 row created. SQL> insert into course_schedule values ("SQL",date "1999-10-04",3,"SEATTLE"); 1 row created. SQL> insert into course_schedule values ("SQL",date "1999-12-13",4,"DALLAS" ); 1 row created. SQL> insert into course_schedule values ("JAV",date "1999-12-13",5,"SEATTLE"); 1 row created. SQL> insert into course_schedule values ("XML",date "2000-02-03",6,"VANCOUVER" ); 1 row created. SQL> insert into course_schedule values ("JAV",date "2000-02-01",7,"DALLAS" ); 1 row created. SQL> insert into course_schedule values ("PLS",date "2000-09-11",8,"VANCOUVER" ); 1 row created. SQL> insert into course_schedule values ("XML",date "2000-09-18",NULL,"SEATTLE"); 1 row created. SQL> insert into course_schedule values ("OAU",date "2000-09-27",9,"DALLAS" ); 1 row created. SQL> insert into course_schedule values ("ERM",date "2001-01-15",10, NULL ); 1 row created. SQL> insert into course_schedule values ("PRO",date "2001-02-19",NULL,"VANCOUVER" ); 1 row created. SQL> insert into course_schedule values ("RSD",date "2001-02-24",8,"CHICAGO"); 1 row created. SQL> SQL> create table employees(
2 empno NUMBER(4) 3 , ename VARCHAR2(8) 4 , init VARCHAR2(5) 5 , job VARCHAR2(8) 6 , mgr NUMBER(4) 7 , bdate DATE 8 , msal NUMBER(6,2) 9 , comm NUMBER(6,2) 10 , deptno NUMBER(2) ) ;
Table created. SQL> SQL> SQL> insert into employees values(1,"Jason", "N", "TRAINER", 2, date "1965-12-18", 800 , NULL, 10); 1 row created. SQL> insert into employees values(2,"Jerry", "J", "SALESREP",3, date "1966-11-19", 1600, 300, 10); 1 row created. SQL> insert into employees values(3,"Jord", "T" , "SALESREP",4, date "1967-10-21", 1700, 500, 20); 1 row created. SQL> insert into employees values(4,"Mary", "J", "MANAGER", 5, date "1968-09-22", 1800, NULL, 20); 1 row created. SQL> insert into employees values(5,"Joe", "P", "SALESREP",6, date "1969-08-23", 1900, 1400, 30); 1 row created. SQL> insert into employees values(6,"Black", "R", "MANAGER", 7, date "1970-07-24", 2000, NULL, 30); 1 row created. SQL> insert into employees values(7,"Red", "A", "MANAGER", 8, date "1971-06-25", 2100, NULL, 40); 1 row created. SQL> insert into employees values(8,"White", "S", "TRAINER", 9, date "1972-05-26", 2200, NULL, 40); 1 row created. SQL> insert into employees values(9,"Yellow", "C", "DIRECTOR",10, date "1973-04-27", 2300, NULL, 20); 1 row created. SQL> insert into employees values(10,"Pink", "J", "SALESREP",null,date "1974-03-28", 2400, 0, 30); 1 row created. SQL> SQL> SQL> SQL> select e.*
2 from employees e
3 where exists (select o.*
4 from course_schedule o
5 where o.course = "SQL"
6 and o.trainer = e.empno);
EMPNO ENAME INIT JOB MGR BDATE MSAL COMM DEPTNO
-------- ----- -------- ---------- --------- ---------- ---------- ----------
1 Jason N TRAINER 2 18-DEC-65 800 10
3 Jord T SALESREP 4 21-OCT-67 1700 500 20
4 Mary J MANAGER 5 22-SEP-68 1800 20
SQL> SQL> drop table employees; Table dropped. SQL> SQL> drop table course_schedule; Table dropped. SQL></source>
not exists and subquery
<source lang="sql">
SQL> SQL> create table offerings
2 ( course VARCHAR2(6) 3 , begindate DATE 4 , trainer NUMBER(4) 5 , location VARCHAR2(8) 6 ) ;
Table created. SQL> insert into offerings values ("SQL",date "2009-04-12",13,"DALLAS" ); 1 row created. SQL> insert into offerings values ("OAU",date "2009-08-10",4,"CHICAGO"); 1 row created. SQL> insert into offerings values ("SQL",date "2009-10-04",1,"SEATTLE"); 1 row created. SQL> insert into offerings values ("SQL",date "2009-12-13",1,"DALLAS" ); 1 row created. SQL> insert into offerings values ("JAV",date "2009-12-13",4,"SEATTLE"); 1 row created. SQL> insert into offerings values ("XML",date "2000-02-03",1,"DALLAS" ); 1 row created. SQL> insert into offerings values ("JAV",date "2000-02-01",11,"DALLAS" ); 1 row created. SQL> insert into offerings values ("PLS",date "2000-09-11",8,"DALLAS" ); 1 row created. SQL> insert into offerings values ("XML",date "2000-09-18",NULL,"SEATTLE"); 1 row created. SQL> insert into offerings values ("OAU",date "2000-09-27",13,"DALLAS" ); 1 row created. SQL> insert into offerings values ("ERM",date "2001-01-15",NULL, NULL ); 1 row created. SQL> insert into offerings values ("PRO",date "2001-02-19",NULL,"DALLAS" ); 1 row created. SQL> insert into offerings values ("RSD",date "2001-02-24",8,"CHICAGO"); 1 row created. SQL> create table registrations
2 ( attendee NUMBER(4) 3 , course VARCHAR2(6) 4 , begindate DATE 5 , evaluation NUMBER(1) 6 , constraint R_PK primary key(attendee,course,begindate) 7 ) ;
Table created. SQL> SQL> insert into registrations values (2,"SQL",date "2009-04-12",4 ); 1 row created. SQL> insert into registrations values (14,"SQL",date "2009-04-12",5 ); 1 row created. SQL> insert into registrations values (6,"SQL",date "2009-04-12",4 ); 1 row created. SQL> insert into registrations values (11,"SQL",date "2009-04-12",2 ); 1 row created. SQL> insert into registrations values (8,"SQL",date "2009-10-04",NULL); 1 row created. SQL> insert into registrations values (9,"SQL",date "2009-10-04",3 ); 1 row created. SQL> insert into registrations values (13,"SQL",date "2009-10-04",4 ); 1 row created. SQL> insert into registrations values (13,"SQL",date "2009-12-13",NULL); 1 row created. SQL> insert into registrations values (6,"SQL",date "2009-12-13",NULL); 1 row created. SQL> insert into registrations values (3,"OAU",date "2009-08-10",4 ); 1 row created. SQL> SQL> select o.*
2 from offerings o 3 where not exists 4 (select r.* 5 from registrations r 6 where r.course = o.course 7 and r.begindate = o.begindate);
COURSE BEGINDATE TRAINER LOCATION
---------- ---------- --------
JAV 13-12-2009 4 SEATTLE XML 03-02-2000 1 DALLAS JAV 01-02-2000 11 DALLAS PLS 11-09-2000 8 DALLAS XML 18-09-2000 SEATTLE OAU 27-09-2000 13 DALLAS ERM 15-01-2001 PRO 19-02-2001 DALLAS RSD 24-02-2001 8 CHICAGO 9 rows selected. SQL> drop table offerings; Table dropped. SQL> drop table registrations; Table dropped. SQL></source>
Not Exist with subquery
<source lang="sql">
SQL> SQL> create table course_schedule
2 ( course VARCHAR2(6) 3 , begindate DATE 4 , trainer NUMBER(4) 5 , location VARCHAR2(20)) ;
Table created. SQL> SQL> SQL> insert into course_schedule values ("SQL",date "1999-04-12",1,"VANCOUVER" ); 1 row created. SQL> insert into course_schedule values ("OAU",date "1999-08-10",2,"CHICAGO"); 1 row created. SQL> insert into course_schedule values ("SQL",date "1999-10-04",3,"SEATTLE"); 1 row created. SQL> insert into course_schedule values ("SQL",date "1999-12-13",4,"DALLAS" ); 1 row created. SQL> insert into course_schedule values ("JAV",date "1999-12-13",5,"SEATTLE"); 1 row created. SQL> insert into course_schedule values ("XML",date "2000-02-03",6,"VANCOUVER" ); 1 row created. SQL> insert into course_schedule values ("JAV",date "2000-02-01",7,"DALLAS" ); 1 row created. SQL> insert into course_schedule values ("PLS",date "2000-09-11",8,"VANCOUVER" ); 1 row created. SQL> insert into course_schedule values ("XML",date "2000-09-18",NULL,"SEATTLE"); 1 row created. SQL> insert into course_schedule values ("OAU",date "2000-09-27",9,"DALLAS" ); 1 row created. SQL> insert into course_schedule values ("ERM",date "2001-01-15",10, NULL ); 1 row created. SQL> insert into course_schedule values ("PRO",date "2001-02-19",NULL,"VANCOUVER" ); 1 row created. SQL> insert into course_schedule values ("RSD",date "2001-02-24",8,"CHICAGO"); 1 row created. SQL> SQL> create table registrations
2 ( attendee NUMBER(4) 3 , course VARCHAR2(6) 4 , begindate DATE 5 , evaluation NUMBER(1)) ;
Table created. SQL> SQL> SQL> insert into registrations values (1, "SQL",date "1999-04-12",4 ); 1 row created. SQL> insert into registrations values (2, "SQL",date "1999-12-13",NULL); 1 row created. SQL> insert into registrations values (3, "SQL",date "1999-12-13",NULL); 1 row created. SQL> insert into registrations values (4, "OAU",date "1999-08-10",4 ); 1 row created. SQL> insert into registrations values (5, "OAU",date "2000-09-27",5 ); 1 row created. SQL> insert into registrations values (6, "JAV",date "1999-12-13",2 ); 1 row created. SQL> insert into registrations values (7, "JAV",date "2000-02-01",4 ); 1 row created. SQL> insert into registrations values (8, "JAV",date "2000-02-01",5 ); 1 row created. SQL> insert into registrations values (9, "XML",date "2000-02-03",4 ); 1 row created. SQL> insert into registrations values (10,"XML",date "2000-02-03",5 ); 1 row created. SQL> insert into registrations values (1, "PLS",date "2000-09-11",NULL); 1 row created. SQL> insert into registrations values (2, "PLS",date "2000-09-11",NULL); 1 row created. SQL> insert into registrations values (3, "PLS",date "2000-09-11",NULL); 1 row created. SQL> SQL> SQL> SQL> select o.*
2 from course_schedule o 3 where not exists 4 (select r.* 5 from registrations r 6 where r.course = o.course 7 and r.begindate = o.begindate);
COURSE BEGINDATE TRAINER LOCATION
--------- ---------- --------------------
SQL 04-OCT-99 3 SEATTLE XML 18-SEP-00 SEATTLE PRO 19-FEB-01 VANCOUVER ERM 15-JAN-01 10 RSD 24-FEB-01 8 CHICAGO SQL> SQL> drop table course_schedule; Table dropped. SQL> SQL> drop table registrations; Table dropped. SQL> SQL></source>
Using the EXISTS Operator with subquery
<source lang="sql">
SQL> CREATE TABLE empExam (
2 empID INT NOT NULL, 3 ExamID INT NOT NULL, 4 Mark INT, 5 Taken SMALLINT, 6 Comments VARCHAR(255), 7 CONSTRAINT PK_empExam PRIMARY KEY (empID, ExamID));
Table created. SQL> SQL> SQL> INSERT INTO empExam (empID,ExamID,Mark,Taken,Comments) VALUES (1,1,55,1,"Satisfactory"); 1 row created. SQL> INSERT INTO empExam (empID,ExamID,Mark,Taken,Comments) VALUES (1,2,73,1,"Good result"); 1 row created. SQL> INSERT INTO empExam (empID,ExamID,Mark,Taken,Comments) VALUES (2,3,44,1,"Hard"); 1 row created. SQL> INSERT INTO empExam (empID,ExamID,Mark,Taken,Comments) VALUES (2,5,39,0,"Simple"); 1 row created. SQL> INSERT INTO empExam (empID,ExamID,Mark,Taken) VALUES (2,6,63,1); 1 row created. SQL> SQL> SQL> SQL> CREATE TABLE emp (
2 empID INT NOT NULL PRIMARY KEY, 3 Name VARCHAR(50) NOT NULL);
Table created. SQL> INSERT INTO emp (empID,Name) VALUES (1,"Tom"); 1 row created. SQL> INSERT INTO emp (empID,Name) VALUES (2,"Jack"); 1 row created. SQL> INSERT INTO emp (empID,Name) VALUES (3,"Mary"); 1 row created. SQL> INSERT INTO emp (empID,Name) VALUES (4,"Bill"); 1 row created. SQL> INSERT INTO emp (empID,Name) VALUES (5,"Cat"); 1 row created. SQL> INSERT INTO emp (empID,Name) VALUES (6,"Victor"); 1 row created. SQL> SQL> SQL> SELECT empID, Name FROM emp s
2 WHERE EXISTS (
3 SELECT empID FROM empExam e
4 WHERE Mark < 40 AND e.empID = s.empID);
EMPID NAME
--------------------------------------------------
2 Jack
1 row selected. SQL> SQL> SQL> SQL> drop table emp; Table dropped. SQL> drop table empExam; Table dropped.</source>
