Oracle Dual Table

Abstract: in this instructional exercise, you will find out about the Oracle DUAL table which is a unique table utilized for assessing articulations or calling functions.

In Oracle, the SELECT proclamation must have a FROM provision. Be that as it may, some queries don’t require any table for example:

For this situation, you may consider making a table and utilize it in the FROM statement for simply utilizing the UPPER() work.

Luckily, Oracle provides you with the DUAL table which is a special table that belongs to the schema of the user SYS but is accessible to all users. The DUAL table has one section named DUMMY whose information type is VARCHAR2() and contains one column with an esteem X.

Oracle DUAL Table

By using the DUAL table, you can call the UPPER() function as follows:

Besides calling built-in function, you can use expressions in the SELECT clause of a query that accesses the DUAL table:

The DUAL table is the most basic one since it was intended for quick access.

In Oracle 10g release 1 or more, Oracle treats the utilization of DUAL the same as calling a function which simply evaluates the expression used in the select rundown. This improvement gives even a superior execution than specifically getting to the physical DUAL table