Is it possible to use SELECT DISTINCT and GROUP BY together? - sql

Question

Is it possible to use SELECT DISTINCT and GROUP BY clause together?
I need DISTINCT to avoid duplicate values and make a single entry of the records, and then get the Total quantity of those duplicate values.
For example, I have columns like Item Name and Quantity and their records are (product A,5), (product A,7).
Since products are the same I want it as a single entry and then total its quantity. So, the output on my report would be like this: (product A,12)
Can DISTINCT and GROUP BY clause solve this together?

Answer 1

Based on your comment on Used_By_Already's answer, I think you need to use sum() over (...) construct, such as the following...
create table [dbo].[Purchases_Supplier] (
[Purchased From] nvarchar(50),
Address nvarchar(50),
[Transaction Month] nvarchar(6),
Category nvarchar(50),
Articles nvarchar(50),
Unit int,
[Unit Price] money,
Qty int,
Tin nvarchar(50),
Cashier nvarchar(50)
);
insert [dbo].[Purchases_Supplier] values
('Acme', '123 Street', '202003', 'Baubles', 'Product A', 1, 1.1, 5, 'Nickel', 'John'),
('Acme', '123 Street', '202003', 'Baubles', 'Product A', 1, 1.1, 7, 'Nickel', 'John'),
('Acme', '123 Street', '202003', 'Baubles', 'Product B', 1, 1.1, 9, 'Silver', 'Maria'),
('Acme', '123 Street', '202003', 'Baubles', 'Product B', 1, 1.1, 11, 'Silver', 'Maria');
declare #Supplier_Name nvarchar(50) = N'Acme',
#Month_Purc nvarchar(6) = '202003',
#Cat nvarchar(50) = 'Baubles';
select
Articles,
Qty,
Unit,
[Unit Price],
[Purchased From],
Address,
Tin,
Cashier,
-- NOTE: partition by has everything in the GROUP BY except [Qty]...
sum(Qty) over (partition by Articles, Unit, [Unit Price], [Purchased From], Address, Tin, Cashier) as Total
from dbo.Purchases_Supplier
where [Purchased From] = #Supplier_Name
and [Transaction Month] = #Month_Purc
and Category = #Cat
group by Articles, Qty, Unit, [Unit Price], [Purchased From], Address, Tin, Cashier;
Which yields the result:
Articles Qty Unit Unit Price Purchased From Address Tin Cashier Total
Product A 5 1 1.1000 Acme 123 Street Nickel John 12
Product A 7 1 1.1000 Acme 123 Street Nickel John 12
Product B 9 1 1.1000 Acme 123 Street Silver Maria 20
Product B 11 1 1.1000 Acme 123 Street Silver Maria 20

Answer 2

GROUP BY will result in distinct rows, it does this automatically, you do NOT also need SELECT DISTINCT to reduce the number of rows.
CREATE TABLE mytable(
product VARCHAR(1) NOT NULL
,quantity INTEGER NOT NULL
);
INSERT INTO mytable(product,quantity) VALUES ('a',7);
INSERT INTO mytable(product,quantity) VALUES ('a',5);
INSERT INTO mytable(product,quantity) VALUES ('b',17);
INSERT INTO mytable(product,quantity) VALUES ('b',15);
select product, sum(quantity) as qty
from mytable
group by product
product | qty
:------ | --:
a | 12
b | 32
db<>fiddle here
Note that there is a single row in that result, i.e. only one row for each distinct value in the column called product because we specified that column in the GROUP BY clause.
db<>fiddle here