How to display result when count=0 for SQL inner join?

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This is a interview SQL test on which stumped me. Here is the question: In every office branch, there is a sales quota to be fulfilled by each salesperson. The SQL query is to display the number of salesperson in each branch that equal or exceed the sales quota. There are 2 tables, Branch and SalesPerson. SalesPerson linked to Branch through BranchID. Branch table has a Quota field to be fulfilled by each SalesPerson's Sales Field.
The SQL commands to create the tables are provided.

SQL

CREATE TABLE [dbo].[Branch](
	[ID] [int] NOT NULL,
	[Quota] [int] NOT NULL
) ON [PRIMARY]
GO

CREATE TABLE [dbo].[SalesPerson](
	[ID] [int] NOT NULL,
	[Name] [nchar](10) NOT NULL,
	[Sales] [int] NOT NULL,
	[BranchID] [int] NOT NULL
) ON [PRIMARY]
GO

The SQL commands to populate the tables are provided below.

SQL

INSERT INTO Branch (ID, Quota) VALUES (1, 500);
INSERT INTO Branch (ID, Quota) VALUES (2, 600);

INSERT INTO SalesPerson (ID, Name, Sales, BranchID) VALUES (1, 'John', 500, 1);
INSERT INTO SalesPerson (ID, Name, Sales, BranchID) VALUES (2, 'Jane', 400, 2);

What I have tried:

SQL

SELECT B.ID AS BranchNum, COUNT(*) AS EligibleSalesPersonCount FROM 
SalesPerson AS S INNER JOIN Branch AS B ON (S.BranchID = B.ID)
WHERE S.Sales >= B.Quota
GROUP BY B.ID;

My Output

BranchNum	EligibleSalesPersonCount
1	        1

Expected Output

BranchNum	EligibleSalesPersonCount
1	        1
2	        0

My question is how to display the result when the EligibleSalesPersonCount is 0?

Posted 26-Jul-20 22:00pm

Shao Voon Wong

Updated 26-Jul-20 23:25pm

v2

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2 solutions

Solution 1

We are more than willing to help those that are stuck: but that doesn't mean that we are here to do it all for you! We can't do all the work, you are either getting paid for this, or it's part of your grades and it wouldn't be at all fair for us to do it all for you.
And interview questions are homework on steroids: it's even less fair for us to answer them as if disadvantages people who can do the job you have applied for.

So we need you to do the work, and we will help you when you get stuck. That doesn't mean we will give you a step by step solution you can hand in!
Start by explaining where you are at the moment, and what the next step in the process is. Then tell us what you have tried to get that next step working, and what happened when you did.

If you can't do this simple task, you really aren't ready to get this job and would fail the interview badly if you did get through this stage.
Good luck with the job hunt, but you need to know the subject before you apply, not after!

Posted 26-Jul-20 22:12pm

OriginalGriff

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Maciej Los · Accepted Answer · 2020-07-26T23:25:00

If i understand you well...

If you would like to display all branches and the number of employees where the sale is bigger-than or equal-to quota for that branch, you need to use different join.

SQL

SELECT B.ID AS BranchNum, COUNT(S.ID) AS EligibleSalesPersonCount
FROM Branch AS B
    LEFT JOIN SalesPerson AS S ON B.BranchID = B.ID  AND S.Sales >= B.Quota
GROUP BY B.ID;

For further details, please see: Visual Representation of SQL Joins[^]

To display corresponding sales-persons:

SQL

SELECT B.ID AS BranchNum, S.*
FROM Branch AS B
    LEFT JOIN SalesPerson AS S ON B.BranchID = B.ID  AND S.Sales >= B.Quota
GROUP BY B.ID;