Dense_rank query in sql(4 different columns) in - sql

Question

I have a table as follows:
Sn no. t_time Value rate
ABC 17-MAY-18 08:00:00 100.00 3
ABC 17-MAY-18 22:00:00 200.00 1
ABC 16-MAY-18 08:00:00 100.00 1
XYZ 14-MAY-18 01:00:00 700.00 1
XYZ 15-MAY-18 10:00:00 500.00 2
XYZ 15-MAY-18 13:00:00 100.00 2
And I want to generate the output as follows:
Sn no. New_value
ABC 150
XYZ 450
It is grouped by the Sn no. The New_value is the latest time of each date value multiplied by rate, and then averaged together.
For example ABC new_value is
Average of:[(100*1) and (200*1)]
Its a large dataset. How do I write a query for the above in the most efficient way. Please help.

Answer 1

You can use analytical function(row_number()) to achieve the result
SQL> WITH cte_table(Snno, t_time, Value, rate) AS (
2 SELECT 'ABC', to_date('2018-05-17 08:00:00', 'YYYY-MM-DD HH24:MI:SS'), 100.00, 3 FROM DUAL UNION ALL
3 SELECT 'ABC', to_date('2018-05-17 22:00:00', 'YYYY-MM-DD HH24:MI:SS'), 200.00, 1 FROM DUAL UNION ALL
4 SELECT 'ABC', to_date('2018-05-16 08:00:00', 'YYYY-MM-DD HH24:MI:SS'), 100.00, 1 FROM DUAL UNION ALL
5 SELECT 'XYZ', to_date('2018-05-14 01:00:00', 'YYYY-MM-DD HH24:MI:SS'), 700.00, 1 FROM DUAL UNION ALL
6 SELECT 'XYZ', to_date('2018-05-15 10:00:00', 'YYYY-MM-DD HH24:MI:SS'), 500.00, 2 FROM DUAL UNION ALL
7 SELECT 'XYZ', to_date('2018-05-15 13:00:00', 'YYYY-MM-DD HH24:MI:SS'), 100.00, 2 FROM DUAL),
8 --------------------------------
9 -- End of data preparation
10 --------------------------------
11 rn_table AS (
12 SELECT t.*, row_number() OVER (PARTITION BY TRUNC(t_time) ORDER BY t_time DESC) AS rn
13 FROM cte_table t)
14 SELECT snno,
15 AVG(VALUE * rate) new_value
16 FROM rn_table
17 WHERE rn = 1
18 GROUP BY snno;
Output:
SNNO NEW_VALUE
---- ----------
ABC 150
XYZ 450

Answer 2

Use the ROW_NUMBER (or RANK/DENSE_RANK if it is more appropriate) analytic function in a sub-query and then aggregate in the outer query:
SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE table_name ( Snno, t_time, Value, rate ) AS
SELECT 'ABC', TIMESTAMP '2018-05-17 08:00:00', 100.00, 3 FROM DUAL UNION ALL
SELECT 'ABC', TIMESTAMP '2018-05-17 22:00:00', 200.00, 1 FROM DUAL UNION ALL
SELECT 'ABC', TIMESTAMP '2018-05-16 08:00:00', 100.00, 1 FROM DUAL UNION ALL
SELECT 'XYZ', TIMESTAMP '2018-05-14 01:00:00', 700.00, 1 FROM DUAL UNION ALL
SELECT 'XYZ', TIMESTAMP '2018-05-15 10:00:00', 500.00, 2 FROM DUAL UNION ALL
SELECT 'XYZ', TIMESTAMP '2018-05-15 13:00:00', 100.00, 2 FROM DUAL;
Query 1:
SELECT snno,
AVG( value * rate ) As new_value
FROM (
SELECT t.*,
ROW_NUMBER() OVER (
PARTITION BY snno, value
ORDER BY t_time DESC
) AS rn
FROM table_name t
)
WHERE rn = 1
GROUP BY snno
Results:
| SNNO | NEW_VALUE |
|------|-------------------|
| ABC | 250 |
| XYZ | 633.3333333333334 |