SQL to find inventory - sql

Question

I am very new to SQL and I have a the following situation:
BTW, "qoh" = "quantity on hand"
product table:
prod_code
qoh
11QER/31
8
13-Q2/P2
32
14-Q1/L3
18
1546-QQ2
15
1558-QW1
23
2232/QTY
8
2232/QWE
6
2238/QPD
12
23109-HB
23
23114-AA
8
54778-2T
43
89-WRE-Q
11
PVC23DRT
188
SM-18277
172
SW-23116
237
WR3/TT3
18
invoiced detail table:
prod_code
quantity-sold
13-Q2/P2
1
23109-HB
1
54778-2T
2
2238/QPD
1
1546-QQ2
1
13-Q2/P2
5
54778-2T
3
23109-HB
2
PVC23DRT
12
SM-18277
3
2232/QTY
1
23109-HB
1
89-WRE-Q
1
13-Q2/P2
2
54778-2T
1
PVC23DRT
5
WR3/TT3
3
23109-HB
1
I want to write a SQL to find out the current inventory, QOH in the product table minus the related item quantity-sold:
prod_code
quantity-sold
13-Q2/P2
0 (8 - 1 - 5 -2)
54778-2T
37 (43 - 2 - 3 - 1)
I tried to use join tables etc and the results did not come out right.
How to write the SQL?
Much appreciated!
Philip

Answer 1

A correlated subquery is a simple what to write this:
select p.*,
p.qoh - (select coalesce(sum(id.quantity_sold), 0)
from invoice_detail id
where id.prod_code = p.prod_code
) as current_inventory
from product p;
It is not clear why your result set has only two products. This version would include all products. And with in index on invoice_detail(prod_code, quantity_sold) should be the fastest method to do what you want.

Answer 2

SELECT
product.prod_code,
prod_code.qoh,
COALESCE( qtySold.total_sold, 0 ) AS qty_sold,
( prod_code.qoh - COALESCE( qtySold.total_sold, 0 ) ) AS current_inventory
FROM
product
LEFT OUTER JOIN
(
SELECT
prod_code,
SUM( quantity_sold ) AS total_sold
FROM
invoiced_detail
GROUP BY
prod_code
) AS qtySold ON
product.prod_code = qtySold.prod_code
ORDER BY
product.prod_code

Answer 3

A left join may be used if you summarized the total quantity sold first and used this as a subquery to join on. See example with your sample data below:
Example
Schema (SQLite v3.30)
CREATE TABLE products (
`prod_code` VARCHAR(8),
`qoh` INTEGER
);
INSERT INTO products
(`prod_code`, `qoh`)
VALUES
('11QER/31', '8'),
('13-Q2/P2', '32'),
('14-Q1/L3', '18'),
('1546-QQ2', '15'),
('1558-QW1', '23'),
('2232/QTY', '8'),
('2232/QWE', '6'),
('2238/QPD', '12'),
('23109-HB', '23'),
('23114-AA', '8'),
('54778-2T', '43'),
('89-WRE-Q', '11'),
('PVC23DRT', '188'),
('SM-18277', '172'),
('SW-23116', '237'),
('WR3/TT3', '18');
CREATE TABLE invoice_details (
`prod_code` VARCHAR(8),
`quantity-sold` INTEGER
);
INSERT INTO invoice_details
(`prod_code`, `quantity-sold`)
VALUES
('13-Q2/P2', '1'),
('23109-HB', '1'),
('54778-2T', '2'),
('2238/QPD', '1'),
('1546-QQ2', '1'),
('13-Q2/P2', '5'),
('54778-2T', '3'),
('23109-HB', '2'),
('PVC23DRT', '12'),
('SM-18277', '3'),
('2232/QTY', '1'),
('23109-HB', '1'),
('89-WRE-Q', '1'),
('13-Q2/P2', '2'),
('54778-2T', '1'),
('PVC23DRT', '5'),
('WR3/TT3', '3'),
('23109-HB', '1');
Query #1
SELECT
p.prod_code,
p.qoh - IFNULL( t1.total_quantity_sold,0) as current_inventory
FROM
products p
LEFT JOIN
(SELECT
id.`prod_code`,
sum(id.`quantity-sold`) as total_quantity_sold
FROM
invoice_details id
GROUP BY
id.prod_code
) t1 ON p.prod_code = t1.prod_code;
prod_code
current_inventory
11QER/31
8
13-Q2/P2
24
14-Q1/L3
18
1546-QQ2
14
1558-QW1
23
2232/QTY
7
2232/QWE
6
2238/QPD
11
23109-HB
18
23114-AA
8
54778-2T
37
89-WRE-Q
10
PVC23DRT
171
SM-18277
169
SW-23116
237
WR3/TT3
15
View on DB Fiddle