Is there a more efficient way to perform this update?
At the moment, despite indices on all the fields concerned, the performance on this is incredible (in a bad way).
Code:
UPDATE TSR_Forecast
SET TSR_Forecast.fc_sales_district_id = b.sales_district_id
FROM TSR_Actuals b
WHERE TSR_Forecast.customernumber = b.apple_hq_id
AND fc_sales_district_id IS NULL
and sales_district_id <> 'SP20'