Applications that allow end users to enter or edit data often need to report errors to their users at the column level. However, the standard server message mechanism makes column-level information available only within the text of the server message. Extended error data provides a means for applications to conveniently access column-level information.
For example, imagine an application that allows end users to enter and edit data in the titleauthor table in the pubs2 database. titleauthor uses a key composed of two columns, au_id and title_id. Any attempt to enter a row with au_id and title_id values that match those in an existing row causes a “duplicate key” message to be sent to the application.
On receiving this message, the application must identify the problem column or columns to the end user so that the user can readily correct them. This information is also available in the text of the duplicate key message, but an application must parse the text to extract the column names.
For information about how to identify and process extended error data, see the “Error and Message Handling” topics page in the Open Client Client-Library/C Reference Manual.
