EXISTS and NOT EXISTS Versus IN and NOT IN : EXISTS « Query Select « Oracle PL/SQL Tutorial

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Oracle PL/SQL Tutorial » Query Select » EXISTS 
2.18.1.EXISTS and NOT EXISTS Versus IN and NOT IN
  1. EXISTS is different from IN.
  2. EXISTS just checks for the existence of rows, whereas IN checks actual values.
  3. EXISTS typically offers better performance than IN with subqueries.
  4. You should use EXISTS rather than IN wherever possible.
  5. When a list of values contains a null, NOT EXISTS returns true, but NOT IN returns false.
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(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, Jobtitlevalues (1,'Tester');

row created.

SQL> insert into job (EMPNO, Jobtitlevalues (2,'Accountant');

row created.

SQL> insert into job (EMPNO, Jobtitlevalues (3,'Developer');

row created.

SQL> insert into job (EMPNO, Jobtitlevalues (4,'COder');

row created.

SQL> insert into job (EMPNO, Jobtitlevalues (5,'Director');

row created.

SQL> insert into job (EMPNO, Jobtitlevalues (6,'Mediator');

row created.

SQL> insert into job (EMPNO, Jobtitlevalues (7,'Proffessor');

row created.

SQL> insert into job (EMPNO, Jobtitlevalues (8,'Programmer');

row created.

SQL> insert into job (EMPNO, Jobtitlevalues (9,'Developer');

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  /

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  /

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  /

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  /

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  /

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  /

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  /

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  /

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  /

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
---------- --------------- --------- ----------- ----------- - ----------
         Jason           25-JUL-96        1234        8767 E          2
         John            15-JUL-97        2341        3456 W          3
         Joe             25-JAN-86        4321        5654 E          3
         Tom             13-SEP-06        2413        6787 W          4
         Jane            17-APR-05        7654        4345 E          4
         James           18-JUL-04        5679        6546 W          5
         Jodd            20-JUL-03        5438        7658 E          6
         Joke            01-JAN-02        8765        4543 W
         Jack            29-AUG-01        7896        1232 E

rows selected.

SQL> select from job
  2  /

     EMPNO JOBTITLE
---------- --------------------
         Tester
         Accountant
         Developer
         COder
         Director
         Mediator
         Proffessor
         Programmer
         Developer

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.
2.18.EXISTS
2.18.1.EXISTS and NOT EXISTS Versus IN and NOT IN
2.18.2.Not Exist with subquery
2.18.3.Exist with subquery
2.18.4.Using the EXISTS Operator with subquery
2.18.5.not exists and subquery
2.18.6.exists in subquery
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