Oracle Dual Table

Topic Introduction: For testing any function or expression we often use DUAL on From clause of a SQL query. today we will discuss what is the DUAL. DUAL is a special DUMMY table of oracle using this we can test any function effect and many other things. as a SQL Query select clause and FROM Clause is a must so we can use the dual table on from clause for any testing. The dual table is designed for fast access.

select * from dual;

select mod(100,3)  from dual;

In this query I have used the Mod function to check the mod result of 100/3 but which would be on from clause. we must need to use a table name. In this case, we can use a dual table.

select 'My name is Reza.' || ' I am a software developer' INFO from dual;

Same case on 2nd query to print out this select statement we use dual table.