Use column name alias during table join
SQL>
SQL> CREATE TABLE departments
2 (department_id number(10) not null,
3 department_name varchar2(50) not null,
4 CONSTRAINT departments_pk PRIMARY KEY (department_id)
5 );
Table created.
SQL>
SQL>
SQL>
SQL> insert into departments ( department_id, department_name )
2 values( 1, 'Data Group' );
1 row created.
SQL>
SQL> insert into departments ( department_id, department_name )
2 values( 2, 'Purchasing' );
1 row created.
SQL>
SQL> insert into departments ( department_id, department_name )
2 values( 3, 'Call Center' );
1 row created.
SQL>
SQL> insert into departments ( department_id, department_name )
2 values( 4, 'Communication' );
1 row created.
SQL>
SQL>
SQL>
SQL> CREATE TABLE employees
2 ( employee_id number(10) not null,
3 last_name varchar2(50) not null,
4 email varchar2(30),
5 hire_date date,
6 job_id varchar2(30),
7 department_id number(10),
8 salary number(6),
9 manager_id number(6),
10 CONSTRAINT employees_pk PRIMARY KEY (employee_id),
11 CONSTRAINT fk_departments FOREIGN KEY (department_id) REFERENCES departments(department_id)
12 );
Table created.
SQL>
SQL>
SQL> insert into employees( employee_id, last_name, email, hire_date, job_id, salary,department_id ,manager_id)
2 values ( 1001, 'Lawson', 'lawson@g.com', '01-JAN-2002','MGR', 30000,1 ,1004);
1 row created.
SQL>
SQL> insert into employees( employee_id, last_name, email, hire_date, job_id, salary, department_id ,manager_id)
2 values ( 1002, 'Wells', 'wells@g.com', '01-JAN-2002', 'DBA', 20000,2, 1005 );
1 row created.
SQL>
SQL> insert into employees( employee_id, last_name, email, hire_date, job_id, salary, department_id ,manager_id)
2 values( 1003, 'Bliss', 'bliss@g.com', '01-JAN-2002', 'PROG', 24000,3 ,1004);
1 row created.
SQL>
SQL> insert into employees( employee_id, last_name, email, hire_date, job_id, salary, department_id, manager_id)
2 values( 1004, 'Kyte', 'tkyte@a.com', SYSDATE-3650, 'MGR',25000 ,4, 1005);
1 row created.
SQL>
SQL> insert into employees( employee_id, last_name, email, hire_date, job_id, salary, department_id, manager_id)
2 values( 1005, 'Viper', 'sdillon@a .com', SYSDATE, 'PROG', 20000, 1, 1006);
1 row created.
SQL>
SQL> insert into employees( employee_id, last_name, email, hire_date, job_id, salary, department_id,manager_id)
2 values( 1006, 'Beck', 'clbeck@g.com', SYSDATE, 'PROG', 20000, 2, null);
1 row created.
SQL>
SQL> insert into employees( employee_id, last_name, email, hire_date, job_id, salary, department_id, manager_id)
2 values( 1007, 'Java', 'java01@g.com', SYSDATE, 'PROG', 20000, 3, 1006);
1 row created.
SQL>
SQL> insert into employees( employee_id, last_name, email, hire_date, job_id, salary, department_id, manager_id)
2 values( 1008, 'Oracle', 'oracle1@g.com', SYSDATE, 'DBA', 20000, 4, 1006);
1 row created.
SQL>
SQL> select * from employees;
EMPLOYEE_ID LAST_NAME EMAIL HIRE_DATE JOB_ID DEPARTMENT_ID SALARY MANAGER_ID
----------- -------------------------------------------------- ------------------------------ --------- ------------------------------ ------------- ---------- ----------
1001 Lawson lawson@g.com 01-JAN-02 MGR 1 30000 1004
1002 Wells wells@g.com 01-JAN-02 DBA 2 20000 1005
1003 Bliss bliss@g.com 01-JAN-02 PROG 3 24000 1004
1004 Kyte tkyte@a.com 13-JUN-98 MGR 4 25000 1005
1005 Viper sdillon@a .com 10-JUN-08 PROG 1 20000 1006
1006 Beck clbeck@g.com 10-JUN-08 PROG 2 20000
1007 Java java01@g.com 10-JUN-08 PROG 3 20000 1006
EMPLOYEE_ID LAST_NAME EMAIL HIRE_DATE JOB_ID DEPARTMENT_ID SALARY MANAGER_ID
----------- -------------------------------------------------- ------------------------------ --------- ------------------------------ ------------- ---------- ----------
1008 Oracle oracle1@g.com 10-JUN-08 DBA 4 20000 1006
8 rows selected.
SQL>
SQL> select * from departments;
DEPARTMENT_ID DEPARTMENT_NA
------------- -------------
1 Data Group
2 Purchasing
3 Call Center
4 Communication
4 rows selected.
SQL>
SQL>
SQL> select employee_id "Emp #", last_name Last,
2 department_name AS "Department"
3 from employees e, departments d
4 where d.department_id = e.department_id
5 and d.department_id = 3
6 /
Emp # LAST Department
---------- -------------------------------------------------- --------------------------------------------------
1003 Bliss Call Center
1007 Java Call Center
SQL>
SQL>
SQL>
SQL> drop table employees cascade constraints;
Table dropped.
SQL> drop table departments cascade constraints;
Table dropped.
SQL>
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