what is the solution of this query? - mysql

Question

I am new to database field. I am currently learning mysql using Murach's Mysql. I came across following problem in the book but I am not able to figure out the correct query for solving it.
Write a SELECT statement that
joins the
Customers, Orders, Order_Items, and
Products tables. This statement should return these columns:
last_name,
first_name,
order_date, product_na
me, item_price, discount_amount,
and
quantity
.
Use aliases for the tables.
Sort the final result set by
last
_name,
order
_date, and
product_name
.
By far I have this query:
select last_name , first_name , order_date , product_name , tem_price,
discount_amount, quantity
from customers , orders , order_items product
order by last_name , order_date , product_name

Answer 1

You can use inner join for these 4 tables Customers , Orders, Order_items , Products but make sure there is a match between the columns in these 3 tables.
Example of the sql query based on the given information. (Assume CustomerID is a match between the columns)
Select A.last_name,A.first_name,B.order_date,B.product_name,C.item_price,C.discount_amount,D.quantity
from TB_Customers A inner join TB_Orders B on A.CustomerID = B.CustomerID
inner join TB_Order_Items C on B.CustomerID = C.CustomerID on
inner join TB_Products D on C.CustomerID = D.CustomerID Where D.CustomerID ='TEST111'

Answer 2

Using ANSI standard join syntax:
SELECT c.last_name, c.first_name, o.order_date, p.product_name,
p.item_price, p.discount_amount, p.quantity
FROM Customers AS c
INNER JOIN Orders AS o ON c.order_id = o.order_id
INNER JOIN Order_Items AS i ON o.order_id = i.order_id
INNER JOIN Products AS p ON i.product_id = p.product_id
ORDER BY c.last _name, o.order _date, p.product_name

Answer 3

Well, we are going to analize the query. Since you didn't specify the database structure, I'm going to do an aproaching.
"SELECT statement that joins the Customers, Orders, Order_Items, and Products tables."
This is refered to the tables, this is in the FROM clause. You have to join them with WHERE clause.
SELECT *
FROM Customers, Orders, Order_Items, Products
WHERE Customers.order_id = Orders.order_id
AND Order_Items.order_id = Orders.order_id
AND Products.product_id = Order_Items.product_id
"This statement should return these columns: last_name, first_name, order_date, product_na me, item_price, discount_amount, and quantity "
This part is refered to the SELECT clause.
SELECT last_name, first_name, order_date, product_name,
item_price, discount_amount, quantity
FROM Customers, Orders, Order_Items, Products
WHERE Customers.order_id = Orders.order_id
AND Order_Items.order_id = Orders.order_id
AND Products.product_id = Order_Items.product_id
"Use aliases for the tables"
This part involves the whole query and means that have to rename the tables (virtually and only form this query) and in every reference you have to use the new name.
SELECT c.last_name, c.first_name, o.order_date, p.product_name,
p.item_price, p.discount_amount, p.quantity
FROM Customers AS c, Orders AS o, Order_Items AS i, Products AS p
WHERE c.order_id = o.order_id
AND i.order_id = o.order_id
AND p.product_id = i.product_id
"Sort the final result set by last _name, order _date, and product_name."
This part refered to th ORDER BY clause. You have to keep in mind the aliases
SELECT c.last_name, c.first_name, o.order_date, p.product_name,
p.item_price, p.discount_amount, p.quantity
FROM Customers AS c, Orders AS o, Order_Items AS i, Products AS p
WHERE c.order_id = o.order_id
AND i.order_id = o.order_id
AND p.product_id = i.product_id
ORDER BY c.last _name, o.order _date, p.product_name