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CREATE TABLE orders(
id INTEGER NOT NULL PRIMARY KEY
,memberid INTEGER NOT NULL
,deliverydate DATE NOT NULL
);
INSERT INTO orders(id,memberid,deliverydate) VALUES (1,991,'2019-10-25');
INSERT INTO orders(id,memberid,deliverydate) VALUES (2,991,'2019-10-26');
INSERT INTO orders(id,memberid,deliverydate) VALUES (3,992,'2019-10-25');
INSERT INTO orders(id,memberid,deliverydate) VALUES (4,992,'2019-10-25');
INSERT INTO orders(id,memberid,deliverydate) VALUES (5,993,'2019-10-24');
INSERT INTO orders(id,memberid,deliverydate) VALUES (7,994,'2019-10-21');
INSERT INTO orders(id,memberid,deliverydate) VALUES (6,994,'2019-10-26');
INSERT INTO orders(id,memberid,deliverydate) VALUES (8,995,'2019-10-26');
select deliverydate first_deliverydate, count(*) cnt
from (
select deliverydate, row_number() over(partition by memberid order by deliverydate) rn
from orders
) t
where rn = 1
group by deliverydate
order by deliverydate
| first_deliverydate | cnt |
|---|---|
| 2019-10-21 | 1 |
| 2019-10-24 | 1 |
| 2019-10-25 | 2 |
| 2019-10-26 | 1 |