Which is NOT a valid source for creating calculated columns using graphical modeling tools?

In the context of graphical modeling tools in SAP HANA, creating calculated columns involves utilizing various sources for deriving new values based on existing data. Valid sources typically include arithmetic manipulations and character manipulations, as they allow developers to perform calculations and transformations directly within the tools. Nesting calculated columns is also permitted, where the output of one calculated column can serve as an input for another, enabling complex computations and data refinement.

However, direct table access is not considered a valid source for creating calculated columns within graphical modeling tools. This is because calculated columns rely on the context of calculations and transformations rather than merely pulling in data from the table. The intention behind calculated columns is to derive values based on other column values using expressions or functions, rather than accessing tables directly in a manner akin to query execution.

Ultimately, the inability to utilize direct table access underscores the emphasis on deriving data through defined calculations rather than through straightforward data retrieval processes. This limitation guides users to design their data models with a clearer separation between data retrieval and data manipulation.