Dual Table

Dual Table:

  • Oracle  database provided a default table called dual table.
  • Dual Table is dummy table mainly it is used for execution purpose.
  • Dual Table has one column and one row dual is also called as an dummy table because it has a dual name called dummy.
  • Dual is not related to table we cannot fetch from table.

Query :  SELECT * form dual;

Query : SELECT  1+1  form dual;

Output : the above query  shows result of 2.

Query : SELECT  1+1  form emp;

Output : the above query  shows result of 2 with 14 rows because emp table contain 14 rows.

Query : SELECT  ename form dual;

Output :  Error invalid identifier.