How do I insert a sum of a column into a table?

Question

I am trying to get the sum of amount from purchases and insert it into the table total_expenses. I don't really understand how to add the values of aggregate functions into other tables as new tuples. Could someone help me on this?

INSERT INTO total_expenses VALUES (Select sum(amount) from purchases);

This procedure gives me "ERROR: syntax error at or near "select""

Answer 1

Don't use the VALUES keyword if the source of your INSERT statement is a SELECT statement. You should also specify your target columns:

INSERT INTO total_expenses (amount) 
select sum(amount) 
from purchases;