Determine external representation

A literal value can appear in SQL statements most anywhere that the binary value can appear. For your opaque-type data to be valid as a literal value in SQL statements, you must define its external representation. It is important that the external representation be reasonably intuitive and easy to enter.

Suppose you need to create an opaque type that holds information about a circle. You can create the external representation that the following figure shows for this circle.

With the external representation in External representation of the circle opaque data type, an INSERT statement can specify a literal value for a column of type circle with the following format:

INSERT INTO tab1 (id_col, circle_col) VALUES (1, "(2, 3, 9)");

Similarly, when an opaque type has an external representation, a client application such as (which displays results as character data) can display a retrieved opaque-type value as part of the output of the following query:

SELECT circle_col FROM tab1 WHERE id_col = 1;

In , the results of this query would display as follows:

(2, 3, 9)