Postgres 13

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE sales (
    id SERIAL PRIMARY KEY,
    event_date DATE,
    customer VARCHAR,
    orderID VARCHAR,
    sales_volume DECIMAL
);

INSERT INTO sales
(event_date, customer, orderID, sales_volume)
VALUES 
('2020-01-08', 'Customer_A', 'Order_001', '130'),
('2020-01-12', 'Customer_A', 'Order_002', '120'),
('2020-01-18', 'Customer_B', 'Order_001', '115'),
('2020-01-22', 'Customer_B', 'Order_002', '300'),
('2020-01-23', 'Customer_B', 'Order_003', '540'),
('2020-01-24', 'Customer_C', 'Order_001', '421'),
('2020-01-26', 'Customer_D', 'Order_001', '198'),

('2020-04-08', 'Customer_B', 'Order_004', '325'),
('2020-04-09', 'Customer_B', 'Order_005', '325'),
('2020-04-11', 'Customer_B', 'Order_006', '425'),
('2020-04-15', 'Customer_D', 'Order_002', '914'),
('2020-04-18', 'Customer_D', 'Order_003', '418'),
('2020-04-20', 'Customer_E', 'Order_001', '723'),
('2020-04-30', 'Customer_C', 'Order_002', '665'),

('2020-06-01', 'Customer_B', 'Order_005', '982'),
('2020-06-15', 'Customer_B', 'Order_006', '100'),
('2020-06-19', 'Customer_C', 'Order_003', '250'),
('2020-06-20', 'Customer_C', 'Order_004', '322'),
('2020-06-30', 'Customer_E', 'Order_002', '924'),
('2020-06-25', 'Customer_A', 'Order_003', '445');

20 rows affected

customer	orderid	event_date	sales_volume
Customer_E	Order_001	2020-04-20	723
Customer_A	Order_002	2020-01-12	120
Customer_B	Order_005	2020-04-09	325
Customer_B	Order_002	2020-01-22	300
Customer_C	Order_003	2020-06-19	250
Customer_A	Order_001	2020-01-08	130
Customer_B	Order_001	2020-01-18	115
Customer_A	Order_003	2020-06-25	445
Customer_E	Order_002	2020-06-30	924
Customer_B	Order_003	2020-01-23	540
Customer_B	Order_004	2020-04-08	325
Customer_D	Order_001	2020-01-26	198
Customer_B	Order_005	2020-06-01	982
Customer_B	Order_006	2020-04-11	425
Customer_C	Order_001	2020-01-24	421
Customer_D	Order_003	2020-04-18	418
Customer_C	Order_004	2020-06-20	322
Customer_B	Order_006	2020-06-15	100
Customer_C	Order_002	2020-04-30	665
Customer_D	Order_002	2020-04-15	914