I have three MySql tables:-
tbl_part - Contains a list of parts with a part_id
tbl_product - Contains a list of products with a product_id
tbl_part_to_product - Contains one to many relationships between parts and products (part_id & product_id)
I'm trying to do two things:-
Select all products that only have one part.
Find all products that only have a specific part as there only part.
SELECT
*
FROM
tbl_part part
INNER JOIN tbl_part_to_product p2p ON part.part_id = p2p.part_id
INNER JOIN tbl_product prod ON p2p.product_id =prod.product_id
WHERE part.name = 'whatever'
GROUP BY prod.product_id
HAVING COUNT(*) = 1
To select all products that only have one part just delete the WHERE clause.
If you don't want to join to the parts table:
SELECT
*
FROM
tbl_product prod
INNER JOIN tbl_part_to_product p2p ON p2p.product_id =prod.product_id
GROUP BY prod.product_id
HAVING COUNT(*) = 1
Let's address both questions:
Select all products that only have one part.
SELECT tbl_product.*
FROM
tbl_product product
INNER JOIN tbl_part_to_product ptop ON ptop.product_id = product.product_id
GROUP BY product.product_id
HAVING COUNT(ptop.part_id) = 1
Find all products that only have a specific part as there only part.
SELECT tbl_product.*
FROM
tbl_product product
INNER JOIN tbl_part_to_product ptop ON ptop.product_id = product.product_id
INNER JOIN tbl_part part ON ptop.part_id = part.part_id
WHERE part.part_name = 'some name'
GROUP BY product.product_id
HAVING COUNT(ptop.part_id) = 1
If you get GROUPing errors from either query, you need to add all the tbl_product fields to the GROUP.
Related
Running the following SELECT query gives unexpectedly two times the same record while there is only 1 product in the database. The are however multiple subcategories linked to the same category, but I still don't understand why this would give two results.
The ERD:
The full contents of the DB:
SELECT p.id AS productId, p.name AS productName FROM product p
INNER JOIN product_base AS pb ON pb.id = p.product_base_id
INNER JOIN product_category AS pc ON pc.id = pb.product_category_id
INNER JOIN product_subcategory AS psc ON psc.product_category_id = pc.id;
Returns:
Why is this product returned two times?
Appending WHERE psc.id = 2 will still give one product as a result, while the intention is that this product should only be found when psc.id = 1.
What am I missing here? Is there something wrong with the structure? How would I get all products that have a certain subcategory?
Would I need to store product_category_id and product_subcategory_id directly in product as well?
#barmar made me realize I am simply missing a direct FK from product to product_subcategory. Otherwise there is of course a missing link between the product and subcategory.
DISTINCT will filter out the duplicates.
SELECT DISTINCT p.id AS productId, p.name AS productName
FROM product p
INNER JOIN product_base AS pb ON pb.id = p.product_base_id
INNER JOIN product_category AS pc ON pc.id = pb.product_category_id
INNER JOIN product_subcategory AS psc ON psc.product_category_id = pc.id;
I have the following tables in my database.I only listed the important columns which can be used for joining.
I need to get the following output
Currently I'm using two seperate queries for each COUNT value
For assigned licenses
select
products.id,products.name,COUNT(assigned_licenses.id)
from
deployment_users
inner join
assigned_licenses
on
deployment_users.id = assigned_licenses.deployment_user_id
inner join
products
on
assigned_licenses.id = products.id
and
deployment_users.customer_id = 10
group by
assigned_licenses.id
;
For total licenses
select
products.id,products.name,COUNT(total_licenses.id)
from
customers
inner join
total_licenses
on
customers.iccode = licenses.iccode
inner join
products
on
total_licenses.id = products.id
and
customers.id = 10
group by
total_licenses.id
;
Since there are more than a 1,000 products that need to be listed,I want to combine them into a single query.How can I do that?
Your specification leaves some room for interpretation (e.g. can a user have assigned licenses without total licenses? if yes my query will fail.) but I would go with this.
SELECT
products.id,
products.name,
Count(Distinct total_licenses.id) As CountTotalLicenses,
Count(Distinct assigned_liceses.deployment_users_id) As CountAssignedLicenses
FROM products
LEFT JOIN total_licenses ON total_licenses.products_id = products.id
LEFT JOIN customers ON customers.iccode = total_licenses.customers_iccode
LEFT JOIN assigned_licenses ON assigned_liceses.total_licenses_id = total_licenses.id
WHERE
customers.id = 10
GROUP BY
products.id,
products.name
For the future it would be awesome if you could paste code as code and not as an image. People cannot simple copy paste snippets of your code and have to type everything again...
Try joining Both of your query
SELECT * FROM (
(First Query) as assigned_licn
INNER JOIN
(Second Query) as total_licn
USING (id)
);
SQL newbie here.
So we have 3 tables:
categories(cat_id,name);
products(prod_id,name);
relationships(prod_id,cat_id);
It is a one-to-many relationship.
So, given a category name say "Books". How do I find all the products that come under books?
As an example,
categories(1,Books);
categories(2,Phones);
products(302,Sherlock Holmes);
relationships(302,1);
You need to JOIN the three tables.
SELECT p.*
FROM relationships r
INNER JOIN products p
ON p.prod_id = r.prod_id
INNER JOIN categories c
ON c.cat_d = r.cat_id
WHERE c.name = 'Books'
You have to join tables on related columns and specify WHERE clause to select all records where category name = 'Books'
SELECT p.*
FROM categories c
JOIN relationships r ON c.cat_id = r.cat_id
JOIN products p ON r.prod_id = p.prod_id
WHERE c.name = 'Books' -- or specify parameter like #Books
In SQL you often join related tables and beginners tend to join, whatever the situation. I would not recommend this. In your case you want to select products. If you only want to show products data, select from products only. You want to select products that are in the category 'Books' (or for which exists an entry in category 'Books'). Hence use an IN or EXISTS clause in order to find them:
select * from products
where prod_id in
(
select prod_id
from relationships
where cat_id = (select cat_id from categories where name = 'Books')
);
Thus you get a well structured query that tells the reader easily how the tables are related and what data you are actually interested in. Later, with different tables and data to select, this may keep you from duplicate result rows that you must get rid of by using DISTINCT or from getting wrong aggregates (sums, counts, etc.), because of mistakenly considering records multifold.
try this:
select p.Prod_id,p.name
from products p inner join relationships r on
p.prod_id = r.prod_id
where r.cat_id = (select cat_id from categories where name = 'books')
or
select p.Prod_id,p.name
from products p inner join relationships r on
p.prod_id = r.prod_id inner join categories c on c.cat_id = r.cat_id
where c.name = 'books'
Note: I have simplified the question since both that and the answer have become I believe more complex than intended.
I want to an an anti-join that has a condition other than just not existing in the first table.
Table Product / Manufacturer
Widget / Acme
Paddle / Acme
Ball / Acme
Gas / Exxon
Pump / Exxon
Table: Customer / Product
Karen / Ball
Bob / Paddle
Karen / Gas
Bob / Pump
A "normal" anti-join would find out which products have not been ordered via
Select Products from `Product / Manufacturer` as T1
Left Join `Customer / Product` as T2
On T2.Zip is NULL
However what I am looking for is which customers didn't order which products, in essence:
Select Products from `Product / Manufacturer`
where Manufacturer = 'Acme' that do not exist in `Customer / Product`
where Customer = 'Karen'
and
Select Products from `Product / Manufacturer`
where Manufacturer = 'Exxon' that do not exist in `Customer / Product`
where Customer = 'Karen'
and
Select Products from `Product / Manufacturer`
where Manufacturer = 'Acme' that do not exist in `Customer / Product`
where Customer = 'Bob'
and
Select Products from `Product / Manufacturer`
where Manufacturer = 'Exxon' that do not exist in `Customer / Product`
where Customer = 'Bob'
'
But as one query since there are 100s of "Customers" and 100s of Manufacturers.
If you want to exclude all products for a manufacturer for which no product from that manufacturer appears in any order...
Then that means that you only want to include only products from certain manufacturers...
Which manufacturers have had a product appear in an order ?
SELECT r.manufacturer
FROM products r
JOIN orders s
ON s.product = r.product
GROUP BY r.manufacturer
You can wrap that query in parens and include it as an inline view ...
SELECT p.*
FROM ( SELECT r.manufacturer
FROM product r
JOIN orders s
ON s.product = r.product
GROUP BY r.manufacturer
) q
JOIN product p
ON p.manufacturer = q.manufacturer
LEFT
JOIN orders o
ON o.product = p.Product
WHERE o.product IS NULL
There are other query patterns that will return an equivalent result.
FOLLOWUP
NOTE: The "breakdown by gender/hour" part wasn't made clear in the original specification.
The query pattern is very much the same. Use an inline view query to return a distinct list of manufacturers for each gender/hour.
Then join that set to the product table, to get every product from those manufacturer. That will included products that were ordered, as well as products that weren't ordered.
Then apply the anti-join pattern, to exclude the products that were ordered by gender/hour.
SELECT q.gender
, q.hour
, p.manufacturer
, p.product
FROM ( SELECT s.gender
, s.hour
, r.manufacturer
FROM orders s
JOIN product r
ON r.product = s.product
GROUP
BY s.gender
, s.hour
, r.manufacturer
) q
JOIN product p
ON p.manufacturer = q.manufacturer
LEFT
JOIN orders o
ON o.gender = q.gender
AND o.hour = q.hour
AND o.product = p.product
WHERE o.product IS NULL
If that's not clear, consider that the following query returns an equivalent set. The inline line view query t returns the set of all products from a manufacturer, by gender/hour.
This query is somewhat less efficient (at least in MySQL) due to the additional inline view. And while longer, it may be more understandable, since the view query t makes explicit the set of all possible rows that could be returned... every product by manufacturer/gender/hour. (To see that set, the view query t can be pulled out and run separately to see what it returns.)
In the outermost query, t is referenced as if it were a table. If it t were replaced by a simple table reference, the query would just be a simple anti-join. All rows from t excluding rows that have a match.
SELECT t.gender
, t.hour
, t.manufacturer
, t.product
FROM (
SELECT q.gender
, q.hour
, q.manufacturer
, p.product
FROM ( SELECT s.gender
, s.hour
, r.manufacturer
FROM orders s
JOIN product r
ON r.product = s.product
GROUP
BY s.gender
, s.hour
, r.manufacturer
) q
JOIN product p
ON p.manufacturer = q.manufacturer
) t
LEFT
JOIN orders o
ON o.gender = t.gender
AND o.hour = t.hour
AND o.product = t.product
WHERE o.product IS NULL
I recommend you get the set of rows returned first. Before you futz with adding a GROUP BY and a GROUP_CONCAT aggregate to collapse the rows.
If you want to group multiple values of "hour" into just "am" or "pm", you can use an expression (in place of "hour") that returns "am" or "pm". (Think in terms of that expression being another column in the table; but instead of referencing a column in the table, you use an expression that derives the value from other columns in the table.
IF(x.hour<12,'am','pm')
I'm trying understand how I can pull information from multiple tables at once in one query if that is possible.
I have 3 tables and I'm wondering if there is a way I can query all the product names for customers that live in california?
Table:
products
Fields:
productOid
productName
companyOid
Table:
customerData
Fields:
customerOid
firstName
lastName
state
Table:
orders
Fields:
orderNumber
customerOid
productOid
Would this fall under something like an INNER JOIN?
Also, I'm learning mySQL.
You will need to use inner joins for this.
SELECT DISTINCT p.productName
FROM orders o
INNER JOIN customerData c ON o.customerOid = c.customerOid
INNER JOIN products p ON o.productOid = p.productOid
WHERE c.state = 'CA';
I am using DISTINCT here because it's possible a customer would order the same product more than once (or multiple customers would order the same products) and I'm assuming you don't want duplicates.
I'm also making the assumption that your state is represented as a two character column.
Read more about joins
You could use one more join, but I would write it this way:
SELECT DISTINCT p.productName
FROM
orders o INNER JOIN products p
ON o.productOid = p.productOid
WHERE
o.customerOid IN (SELECT customerOid
FROM customerData
WHERE state = 'California')
It might be a little slover than a join, but it's more readable.
This shows products that CA customers have ordered:
SELECT p.productName
FROM orders o
INNER JOIN products p ON o.productOid = p.productOid
INNER JOIN customerData c ON o.customerOid = c.customerOid
WHERE c.state = 'CA'