SQL Exercises: Find all customers with orders on October 5, 2012

SQL Query on multiple tables : Exercise-8 with Solution

From the following table, write a SQL query to find those customers who placed orders on October 5, 2012. Return customer_id, cust_name, city, grade, salesman_id, ord_no, purch_amt, ord_date, customer_id and salesman_id.

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: orders

ord_no      purch_amt   ord_date    customer_id  salesman_id
----------  ----------  ----------  -----------  -----------
70001       150.5       2012-10-05  3005         5002
70009       270.65      2012-09-10  3001         5005
70002       65.26       2012-10-05  3002         5001
70004       110.5       2012-08-17  3009         5003
70007       948.5       2012-09-10  3005         5002
70005       2400.6      2012-07-27  3007         5001
70008       5760        2012-09-10  3002         5001
70010       1983.43     2012-10-10  3004         5006
70003       2480.4      2012-10-10  3009         5003
70012       250.45      2012-06-27  3008         5002
70011       75.29       2012-08-17  3003         5007
70013       3045.6      2012-04-25  3002         5001

Sample Solution:

-- This query selects all columns ('*') from the 'customer' table (aliased as 'a') and the 'orders' table (aliased as 'b').
-- It retrieves data where the 'customer_id' column in the 'a' table (customer) matches the 'customer_id' column in the 'b' table (orders),
-- and the 'ord_date' column in the 'b' table is equal to '2012-10-05'.
SELECT *
-- Specifies the tables from which to retrieve the data (in this case, 'customer' aliased as 'a' and 'orders' aliased as 'b').
FROM customer a, orders b
-- Specifies the conditions for joining the tables and filtering the data.
WHERE a.customer_id = b.customer_id
  AND b.ord_date = '2012-10-05';

Output of the Query:

customer_id	cust_name	city		grade	salesman_id	ord_no	purch_amt	ord_date	customer_id	salesman_id
3002		Nick Rimando	New York	100	5001		70002	65.26		2012-10-05	3002		5001
3005		Graham Zusi	California	200	5002		70001	150.50		2012-10-05	3005		5002

Code Explanation:

The said query in SQL that performs a join between two tables: 'customer' and 'orders'. It returns all columns (*) from both tables where the customer_id column in table 'customer' matches the customer_id column in table 'orders' and the ord_date in table 'orders' is equal to '2012-10-05'.

Relational Algebra Expression:

Relational Algebra Tree:

Explanation:

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