Programming Oracle® Triggers and Stored Procedures, Third Edition

2.14. DUAL

Literal expressions can be used within the select clause of a select statement. For example, if we have a table, PROFESSORS, with a column called SALARY, we can select all salaries plus what those salaries would be with a 10% increase.

SELECT SALARY, SALARY*1.1 FROM professors;

We can use SQL and built-in functions to do some math. To get the square root of 2, we can execute the following select statement.

SELECT SQRT(2) FROM professors;

This select will return the square root of 2 for every row in the table. If the table has just one row, then we will get the square root of 2 once. Why not create a dummy table to use with these expressions? This already exists. It is called DUAL. It is not declared in your schema, but it is in ...