feat: merge into returns how many rows update/delete/inserted

[BohuTANG]

Summary

[JackTan25]

well, I think we should change merge into to output a table.

[BohuTANG]

It's not status, it's a result table as COPY INTO returns.

[BohuTANG]

well, I think we should change merge into to output a table.

But note that the output table columns is dynamic adjust by the MERGE clause which cases have.
If we have this, the wizard also can check the MERGE INTO returns table.

[JackTan25]

well, I think we should change merge into to output a table.

But note that the output table columns is dynamic adjust by the MERGE clause which cases have. If we have this, the wizard also can check the MERGE INTO returns table.

yes, it means when once is zero, we shouldn't output it.

[JackTan25]

let's close this one. we have done it in #13903