An invisible column is a user-specified column whose values are only visible when the column is explicitly specified by name. You can add an invisible column to a table without affecting existing applications, and make the column visible if necessary.

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In general, invisible columns help migrate and evolve online applications. A use case might be an application that queries a three-column table with a SELECT * statement. Adding a fourth column to the table would break the application, which expects three columns of data. Adding a fourth invisible column makes the application function normally. A developer can then alter the application to handle a fourth column, and make the column visible when the application goes live.

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The following example creates a table products with an invisible column count, and then makes the invisible column visible:

CopyCREATE TABLE products ( prod_id INT, count INT INVISIBLE );
ALTER TABLE products MODIFY ( count VISIBLE );

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See also

• Oracle Database Administrator’s Guide to learn how to manage invisible columns
• Oracle Database SQL Language Reference for more information about invisible columns

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