Performing SELECT Statements that Use Two Tables : Introduction « Table Joins « Oracle PL/SQL Tutorial

Oracle PL/SQL Tutorial
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2. Query Select
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Oracle PL/SQL Tutorial » Table Joins » Introduction 
7. 1. 4. Performing SELECT Statements that Use Two Tables

To join two tables means that you specify both the tables in the query's FROM clause.

And Use related columns from each table.

The related columns could be a foreign key from one table and the primary key from another table.

You use an operator, such as the equality operator (=), in the query's WHERE clause.

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  )
  9  /

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)
  2               values (1,      'Jason', to_date('19960725','YYYYMMDD'), 1234,              8767,         'E')
  3  /

row created.

SQL> insert into Employee(EMPNO,  EName,   HIREDATE,                       ORIG_SALARY,       CURR_SALARY,  REGION)
  2               values (2,      'John',  to_date('19970715','YYYYMMDD'), 2341,              3456,         'W')
  3  /

row created.

SQL> insert into Employee(EMPNO,  EName,   HIREDATE,                       ORIG_SALARY,       CURR_SALARY,  REGION)
  2               values (3,      'Joe',   to_date('19860125','YYYYMMDD'), 4321,              5654,         'E')
  3  /

row created.

SQL> insert into Employee(EMPNO,  EName,   HIREDATE,                       ORIG_SALARY,       CURR_SALARY,  REGION)
  2               values (4,      'Tom',   to_date('20060913','YYYYMMDD'), 2413,              6787,         'W')
  3  /

row created.

SQL> insert into Employee(EMPNO,  EName,   HIREDATE,                       ORIG_SALARY,       CURR_SALARY,  REGION)
  2               values (5,      'Jane',  to_date('20050417','YYYYMMDD'), 7654,              4345,         'E')
  3  /

row created.

SQL> insert into Employee(EMPNO,  EName,   HIREDATE,                       ORIG_SALARY,       CURR_SALARY,  REGION)
  2               values (6,      'James', to_date('20040718','YYYYMMDD'), 5679,              6546,         'W')
  3  /

row created.

SQL> insert into Employee(EMPNO,  EName,   HIREDATE,                       ORIG_SALARY,       CURR_SALARY,  REGION)
  2               values (7,      'Jodd',  to_date('20030720','YYYYMMDD'), 5438,              7658,         'E')
  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
---------- --------------- --------- ----------- ----------- -
         Jason           25-JUL-96        1234        8767 E
         John            15-JUL-97        2341        3456 W
         Joe             25-JAN-86        4321        5654 E
         Tom             13-SEP-06        2413        6787 W
         Jane            17-APR-05        7654        4345 E
         James           18-JUL-04        5679        6546 W
         Jodd            20-JUL-03        5438        7658 E
         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>
SQL> SELECT employee.ename, job.jobtitle
  2  FROM employee, job
  3  WHERE employee.empno = job.empno;

ENAME           JOBTITLE
--------------- --------------------
Jason           Tester
John            Accountant
Joe             Developer
Tom             COder
Jane            Director
James           Mediator
Jodd            Proffessor
Joke            Programmer
Jack            Developer

rows selected.

SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /

Table dropped.

SQL> drop table job
  2  /

Table dropped.

SQL>
7. 1. Introduction
7. 1. 1. Performing SELECT Statements that Use More than Two Tables
7. 1. 2. Three different types of joins:
7. 1. 3. Understanding Non-equijoins
7. 1. 4. Performing SELECT Statements that Use Two Tables
7. 1. 5. Example simple join.
7. 1. 6. Use table alias in table join
7. 1. 7. Convert subqueries to JOINs
7. 1. 8. autotrace ansi full outer join
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