Chapter 12 Creating Mappings
When an operation implies action on the database, like data retrieval or data update, you can associate this operation with a SQL query that will execute an action in the database. Usually, this query is a SELECT statement used to retrieve one or several instances of the current class according to the operation parameter. It can also be an UPDATE query. In the context of an EJB, the SQL query mapped to an operation is used to implement finder or select methods.
This query is automatically computed to figure out how to retrieve or update data in the database. If you modify the SQL query, it becomes user-defined and can no longer be automatically calculated, even when you update the mapping. You can tell that a statement is user-defined because the User-Defined tool is pressed in the toolbar.
You can recover the computed expression by clicking the User-Defined tool, this will remove any non calculated expression from the page.
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