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How to insert the data  using an entity with ID generation as sequence, and insert data using sql in it?

so as the data just added manually does not overwrites those added via queries.

In this approach, external loads are handled using the SQL interface. It works as follows:

The external load is initialized using a function call to the GET_NEW_LOADID function on the repository schema. This function call returns a Load ID.

SD (SA for Basic Entities) tables are loaded using SQL inserts issued on the data location schema.

The external load is submitted or cancelled using function calls on the repository schema:

SUBMIT_LOAD to submit a load identified by its Load ID. This function call returns a Batch ID.

Also,

You will have to select the Sequence of your entity properly when you INSERT in SQL, to keep a sync between SQL and GUI.