SQL Exercise: A list of which salesmen work for which customers

SQL JOINS: Exercise-3 with Solution

From the following tables write a SQL query to find the salesperson(s) and the customer(s) he represents. Return Customer Name, city, Salesman, commission.

Sample table: customer

 customer_id |   cust_name    |    city    | grade | salesman_id 
-------------+----------------+------------+-------+-------------
        3002 | Nick Rimando   | New York   |   100 |        5001
        3007 | Brad Davis     | New York   |   200 |        5001
        3005 | Graham Zusi    | California |   200 |        5002
        3008 | Julian Green   | London     |   300 |        5002
        3004 | Fabian Johnson | Paris      |   300 |        5006
        3009 | Geoff Cameron  | Berlin     |   100 |        5003
        3003 | Jozy Altidor   | Moscow     |   200 |        5007
        3001 | Brad Guzan     | London     |       |        5005

Sample table: salesman

 salesman_id |    name    |   city   | commission 
-------------+------------+----------+------------
        5001 | James Hoog | New York |       0.15
        5002 | Nail Knite | Paris    |       0.13
        5005 | Pit Alex   | London   |       0.11
        5006 | Mc Lyon    | Paris    |       0.14
        5007 | Paul Adam  | Rome     |       0.13
        5003 | Lauson Hen | San Jose |       0.12

Sample Solution:

-- Selecting specific columns and renaming them for clarity
SELECT a.cust_name AS "Customer Name", 
       a.city, 
       b.name AS "Salesman", 
       b.commission 
-- Specifying the tables to retrieve data from ('customer' as 'a' and 'salesman' as 'b')
FROM customer a 
-- Performing an inner join based on the salesman_id
INNER JOIN salesman b 
ON a.salesman_id = b.salesman_id;

Output of the Query:

Customer Name	city		Salesman	commission
Nick Rimando	New York	James Hoog	0.15
Brad Davis	New York	James Hoog	0.15
Graham Zusi	California	Nail Knite	0.13
Julian Green	London		Nail Knite	0.13
Fabian Johnson	Paris		Mc Lyon		0.14
Geoff Cameron	Berlin		Lauson Hen	0.12
Jozy Altidor	Moscow		Paul Adam	0.13
Brad Guzan	London		Pit Alex	0.11

Explanation:

The said SQL query that is used to select specific columns from two tables, customer and salesman, and join them using the 'salesman_id' column. The query selects the 'cust_name' column from the customer table as 'Customer Name', the 'city' column from the customer table, the 'name' column from the salesman table as 'Salesman', and the 'commission' column from the salesman table.
The query uses an inner join, which only returns rows where there is a match in both tables on the specified join column.

Visual Explanation:

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Query Visualization:

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