SQL Exercises: Customers along with the salesmen who works for them

SQL Query on Multiple Tables: Exercise-2 with Solution

From the following tables, write a SQL query to locate all the customers and the salesperson who works for them. Return customer name, and salesperson name.

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:

-- This query selects specific columns ('customer.cust_name' and 'salesman.name') from the 'customer' and 'salesman' tables.
-- It retrieves data where the 'salesman_id' column in the 'salesman' table matches the 'salesman_id' column in the 'customer' table.
SELECT customer.cust_name, salesman.name
-- Specifies the tables from which to retrieve the data (in this case, 'customer' and 'salesman').
FROM customer, salesman
-- Specifies the condition for joining the 'customer' and 'salesman' tables based on the equality of the 'salesman_id' columns.
WHERE salesman.salesman_id = customer.salesman_id;

Output of the query:

cust_name	name
Nick Rimando	James Hoog
Brad Davis	James Hoog
Graham Zusi	Nail Knite
Julian Green	Nail Knite
Fabian Johnson	Mc Lyon
Geoff Cameron	Lauson Hen
Jozy Altidor	Paul Adam
Brad Guzan	Pit Alex

Code Explanation:

The given query in SQL that joins the 'customer' and 'salesman' tables based on the "salesman_id" column. The result set includes the customer name (cust_name) and salesman name (name). The WHERE clause specifies the join condition between the two tables, which is that the "salesman_id" column must be equal in both tables.

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