SQL Exercise: Customers who holds a grade less than 300

SQL JOINS: Exercise-9 with Solution

From the following tables write a SQL query to find those customers with a grade less than 300. Return cust_name, customer city, grade, Salesman, salesmancity. The result should be ordered by ascending customer_id.

Sample table: customer

Sample table: salesman

Sample Solution:

SELECT a.cust_name,a.city,a.grade, 
b.name AS "Salesman", b.city 
FROM customer a 
LEFT OUTER JOIN salesman b 
ON a.salesman_id=b.salesman_id 
WHERE a.grade<300 
ORDER BY a.customer_id;

Output of the Query:

cust_name	city		grade	Salesman	city
Nick Rimando	New York	100	James Hoog	New York
Jozy Altidor	Moscow		200	Paul Adam	Rome
Graham Zusi	California	200	Nail Knite	Paris
Brad Davis	New York	200	James Hoog	New York
Geoff Cameron	Berlin		100	Lauson Hen	San Jose

Explanation:

The said SQL query is selecting the customer name, city, and grade from the customer table aliased as a and the salesman name and city from the salesman table aliased as b.
It is joining these tables on the 'salesman_id' column and only selecting the customers whose grade is less than 300.
The results are ordered by the 'customer_id' column.
Additionally, it is using a LEFT OUTER JOIN which will retrieve all records from the left table and the matching records from the right table. If no match is found on the right table, it will return NULL for the right table's fields.

Visual Explanation:

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Query Visualization:

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