Use table name to reference column name : Columns « Query Select « Oracle PL/SQL Tutorial

SQL>
SQL> CREATE TABLE emp (
  2    emp_id               NUMBER,
  3    ename             VARCHAR2(40),
  4    hire_date        DATE DEFAULT sysdate,
  5    end_date DATE,
  6    rate     NUMBER(5,2),
  7    CONSTRAINT emp_pk    PRIMARY KEY (emp_id)
  8  );

Table created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (101, 'Mary', to_date('15-Nov-1961','dd-mon-yyyy'),null,169);

1 row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (102, 'Tom', to_date('16-Sep-1964','dd-mon-yyyy'),to_date('5-May-2004','dd-mon-yyyy'),135);

1 row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (104, 'Peter', to_date('29-Dec-1987','dd-mon-yyyy'),to_date('1-Apr-2004','dd-mon-yyyy'),99);

1 row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (105, 'Mike', to_date('15-Jun-2004','dd-mon-yyyy'),null,121);

1 row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (107, 'Less', to_date('2-Jan-2004','dd-mon-yyyy'),null,45);

1 row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (108, 'Park', to_date('1-Mar-1994','dd-mon-yyyy'),to_date('15-Nov-2004','dd-mon-yyyy'),220);

1 row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (110, 'Ink', to_date('4-Apr-2004','dd-mon-yyyy'),to_date('30-Sep-2004','dd-mon-yyyy'),84);

1 row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (111, 'Tike', to_date('23-Aug-1976','dd-mon-yyyy'),null,100);

1 row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (112, 'Inn', to_date('15-Nov-1961','dd-mon-yyyy'),to_date('4-Apr-2004','dd-mon-yyyy'),70);

1 row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (113, 'Kate', to_date('3-Mar-2004','dd-mon-yyyy'),to_date('31-Oct-2004','dd-mon-yyyy'),300);

1 row created.

SQL>
SQL> SET ECHO ON
SQL> SELECT emp.emp_id, emp.ename
  2  FROM emp;
       101 Mary
       102 Tom
       104 Peter
       105 Mike
       107 Less
       108 Park
       110 Ink
       111 Tike
       112 Inn
       113 Kate

10 rows selected.

SQL>
SQL>
SQL> drop table emp;

Table dropped.

2.8.Columns
	2.8.1.	Selecting All Columns from a Table with asterisk character (*)
	2.8.2.	Count(*) and column renaming
	2.8.3.	Expression and column renaming
	2.8.4.	DISTINCT tableName.*
	2.8.5.	Combined columns and renaming
	2.8.6.	Format date value and column renaming
	2.8.7.	Reference one column more than once
	2.8.8.	Reference renamed column in order by
	2.8.9.	Rename case when column
	2.8.10.	Returning Multiple Columns
	2.8.11.	Table renaming in from clause
	2.8.12.	Use table name to reference column name