What is a limitation when creating an external view in SAP HANA?

When creating an external view in SAP HANA, using the ABAP Development Tools (ADT) is indeed a necessity. ADT provides the necessary environment and functionalities to define and manage external views effectively within the ABAP programming model. This integration helps ensure that developers leverage the full capabilities and features provided by the ABAP framework while interacting with HANA views.

Utilizing ADT allows developers to employ best practices, adhere to standards, and maintain consistency across development efforts, creating a seamless experience for working with SAP HANA data models in conjunction with ABAP applications.

Other aspects, like the need to know underlying tables and join conditions or the limitations on SQL usage, may affect how one interacts with views but do not inherently relate to the requirement of using ADT for external view creation. Therefore, the necessity of adopting ADT is a fundamental limitation recognized when setting up external views in SAP HANA.