If the column is imported, the properties of the column are set automatically. The following list contains information about nullable and data type values for columns imported into the Physical layer.
- Nullable. The option Nullable in the Physical Columns dialog box indicates whether null values are allowed for the column. If null values can exist in the underlying table, you need to select this option. This allows null values to be returned to the user, which is expected with certain functions and with outer joins. It is generally safe to change a non-nullable value to a nullable value in a physical column.
- Data type. The data type list indicates the data type of the columns. Use caution in changing the data type values. Setting the values to ones that are incorrect in the underlying data source might cause unexpected results. If there are any data type mismatches, correct them in the repository or reimport the columns with mismatched data types. If you reimport columns, you also need to remap any logical column sources that reference the remapped columns. The data type of a logical column in the business model must match the data type of its physical column source. The Oracle BI Server will pass these logical column data types to client applications.