Expression Type property

Select an Expression Type to indicate how the value of the Calculated Field must be determined:

This table shows the available Expression Types:


Expression Type	Description
Simple Expression	Use this Expression Type if the table data is already available. The data is available if the used table fields in the Simple Expression are part of: The main table of the session. A table that is linked with the Table property For a Simple Expression, you must fill the Simple Expression property.
Query Extension	Use this Expression Type if the table data is not yet available but can be added to the session’s query as an inner join. The complete query extension (`Select`, `From` and `Where` properties) must be specified to determine the value of the Calculated Field. Use this Expression Type if you are sure the data read by the query extension exists. If you cannot be sure that the data exists, use the `Nested Select` Expression Type. You cannot use this Expression Type if you need aggregated values (`count`, `average`, etc.). For aggregations, you must use the `Nested Select` Expression Type.
Nested Select	Use this Expression Type if the data is not yet available and an inner join is not possible, because the data may not be present. This Expression Type is also required for aggregations of table data. The complete query (`Select`, `From` and `Where`) must be coded in the `Select` property.
Function	Use this Expression Type if the calculation of the field cannot be expressed in a query. For example, a complex calculation or a web service call. Note that Calculated Fields with Expression Type “Function” are not enabled for (easy) filtering.