On a similar note do you have much experience with datawarehousing vs. OLTP?

I'd go with librarian, the skills are pretty similar, organizing data for efficient storage and retrieval, worrying about securing access to important information and preventing data loss.

If this is an SSIS package just add a SQL step to truncate the target table before loading it.

You could try adding technical_details_id to this index.

CREATE NONCLUSTERED INDEX [IX_tbTechnical_Details_sp_ref_no_incl] ON [dbo].[tbTechnical_Details]

(
technical_details_id,
[spt_ref_no] ASC

)

INCLUDE ( [mozart_ref_no]

)