I am trying to fetch maximum balance for given account
ACCT_BALANCE table:
ACCOUNT_JOIN,BALANCE_UPDATE_DATE,ACCT_VALUE
1 11:49 AM 3/21/2017 1000
1 10:49 AM 5/29/2017 2121
2 11:49 AM 3/29/2017 3332
2 13:21 AM 3/33/2017 110
3 11:50 AM 4/4/2017 888
4 10:49 AM 3/29/2017 66
4 11:50 AM 3/3/2017 57000
4 10:49 AM 2/29/2017 2265
4 13:21 AM 3/2/2017 555
4 11:50 AM 8/9/2017 555
for example, max balance for account join 1 is 2121 from 5/29/2017
Performance wise what will be better? using MAX with Inner join or rank() over?
CREATE OR REPLACE VIEW MAX_VAL_VIEW
AS
SELECT ACCT_VALUE,ACCOUNT_JOIN
FROM (
SELECT ACCT_VALUE,ACCOUNT_JOIN,
rank() over (partition by ACCOUNT_JOIN order by BALANCE_UPDATE_DATE desc) rnk
FROM ACCT_BALANCE
)
WHERE rnk = 1
/
CREATE OR REPLACE VIEW MAX_VAL_VIEW
AS
SELECT A.ACCT_VALUE ,A.ACCOUNT_JOIN
FROM ACCT_BALANCE A
WHERE A.BALANCE_UPDATE_DATE = (
SELECT max(B.BALANCE_UPDATE_DATE)
FROM ACCT_BALANCE B
WHERE B.ACCOUNT_JOIN = A.ACCOUNT_JOIN
)
/
You could also use the last
function:
select max(acct_value) keep (dense_rank last order by balance_update_date) as acct_value,
account_join
from acct_balance
group by account_join;
ACCT_VALUE ACCOUNT_JOIN
---------- ------------
2121 1
110 2
888 3
555 4
(using modified date/times to make them all valid).
Either that or the rank()
approach should beat the max(B.BALANCE_UPDATE_DATE)
approach, as they only hit the table once. You can look at the execution plans for all three queries to see how the optimiser treats them - which indexes (if any) they use, how many full table scans, etc.