Question

I have 2 tables — a master and details. It’s a 1-to-many relationship between master and details.

Amongst many other columns, the master table has:

id column (index)
total column

Amongst many other columns, the details table has:

id column (index)
value column

What might the SQL UPDATE statement look like to join these 2 tables together and UPDATE master.total with the sum of details.value where master.id = details.id

Thanks your help.

Answer 1

update master as m 
set total=
(select sum(value) from detail as d where d.id=m.id)