On 1/1/19 11:05 AM, Chuck Martin wrote:
Sorry if this is too basic a question for this list, but I don't fully
get how to use aggregates (sum()) and group-by together. I'm trying to
get a list of transactions where the total for a given account exceeds a
given number. I'm not sure an example is needed, but if so, consider
this simplified data:
accountid. name
1 bill
2. james
3 sarah
4 carl
transaction
id. amount. accountid. name
1. 50. 1 bill
2. 25. 2 james
3 35 4 carl
4. 75. 1 bill
5 25. 1 bill
6 50 3 sarah
results wanted-all transactions where account total >= 50
id. amount. accountid. name
1. 50. 1 bill
3. 75. 1 bill
4 25. 1 bill
5 50 3 sarah
I've tried to understand how to use GROUP BY and HAVING, but the penny
won't drop. I keep getting errors saying that all columns in the SELECT
have to also be in the GROUP BY, but nothing I've done seems to produce
the correct results. I think because the GROUP BY contains multiple
columns, so each row is treated as a group. It also is difficult to
parse out since in the real world, many more tables and columns are
involved.
Window Functions?:
https://www.postgresql.org/docs/11/tutorial-window.html
Or do something like(untested):
select transactionid, amount, accountid, name from transaction join
(select accountid, sum(amount) from transaction group by(accountid)) as
account_sum on transaction.transactionid = account_sum.accountid and
account_sum.sum >= 50
Chuck Martin
Avondale Software
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
