How to use if updating on nested column in triggers
For each nested collection selected by the DML statement, the following steps are performed when the trigger code includes references to parent values: determining the row, within the view, in which the nested collection resides and, prior to executing the trigger code for the nested collection, binding the one or more references to one or more corresponding values that logically reside in the row.In a database management system (DBMS), data is stored in one or more data containers, each container contains records, and the data within each record is organized into one or more fields.One type of view that is generally not updateable is a view that is used to present data in the form of a virtual table with a nested collection column.The base data for the nested collections, and for the other columns of the virtual parent table that contains the nested collections, may actually have been gathered by the database server from multiple base tables.In relational database systems, the data containers are referred to as tables, the records are referred to as rows, and the fields are referred to as columns.In object oriented databases, the data containers are referred to as object classes, the records are referred to as objects, and the fields are referred to as attributes.The view definition contains mappings to one or more columns in the one or more tables containing the data.
Individual items in the nested collections of dept_emp can be modified using the TABLE( ) clause.
Typically, the view definition is in the form of a database query. Within each row, the emplist column has a nested collection.
For example, a view dept_view that has a row for each department, where the row for a particular department has one column for the department number, one column for department name, and one nested collection column that includes the names of all the employees that belong to the department, may be defined by the following statement: A view that may be created in response to this definition is illustrated in FIG. In dept_view 100, each nested collection is a virtual table that contains three columns.
Other database architectures may use other terminology.
Systems that implement the present invention are not limited to any particular type of data container or database architecture.
The structure of dept_view 100 is dictated by its view definition.