This is a question I got from a book (don't remember which), it goes like this:
You have three tables:
Supplier (supId, name)
Product (prodId, name)
inventory (supId, prodId)
You need to find, with one query, all the suppliers that have in their inventory all the products (or more) supplier X has (lets say supplier X is the one with supId=1).
(so if supplier 1 has in his inventory bananas and apples, you need to find all the suppliers that carry at least bananas and apples)
You can use standard SQL only (including joins).
Apparently this is a known issue/question, you should check out this question:
How to filter SQL results in a has-many-through relation
(excellent solutions and analysis)
That problem is known as relational division.
One solution is double negation. You can select all suppliers, for whom no product delivered by supplier X exists, that is not delivered by them:
select distinct other_supplier.SupID
from Inventory other_supplier
where not exists
(
select *
from Inventory supplier_X
where supplier_X.supId = 1 -- For supplier X
and not exists
(
select *
from Inventory other_product
where other_supplier.supId = other_product.Supid
and supplier_X.prodId = other_product.prodId
)
)
Live example at SQL Fiddle.
I believe this solution uses standard SQL, except for the parameter definition.
DECLARE #supplierX int = 4
SELECT
[s].[supid],
[s].[name]
FROM [Inventory] [i1]
INNER JOIN [Inventory] [i2] ON [i1].[prodid] = [i2].[prodid]
INNER JOIN [Supplier] [s] ON [i1].[supid] = [s].[supid]
WHERE
[i1].[supid] <> #supplierX
AND [i2].[supid] = #supplierX
GROUP BY
[s].[supid],
[s].[name]
HAVING
COUNT(*) >= (SELECT COUNT(*) FROM [Inventory] [i3] WHERE [i3].[supid] = #supplierX)
A Fiddle is found here.
A breakdown of the query above:
Determine the number of products supplierX has in it's inventory (count(*))
Determine the products other suppliers share with supplierX (join by prodid)
Make sure the number of shared products is higher than or equal to the number of products supplierX has in it's inventory (HAVING COUNT() >= ...)
Related
please provide some assistance/guidance to solve the following:
I have 1 main table which indicates sales volumes by sales person per different product type.
Where a salesperson did not sell a particular product on a particular day, there is no record.
The intention is to create null value records for salesmen that did not sell a product on a specific day. The query must be dynamic as there are many more salesmen with sales over many days.
Thanks in advance
Just generate records for all sales persons, days, and products using cross join and then bring in the existing data:
select p.salesperson, d.salesdate, st.salestype,
coalesce(t.sales_volume, 0)
from (select distinct salesperson from t) p cross join
(select distinct salesdate from t) d cross join
(select distinct salestype from t) st left join
t
on t.salesperson = p.salesperson and
t.salesdate = d.salesdate and
t.salestype = st.salestype;
Note: You may have other tables that have lists of sales people, dates, and types -- and those can be used instead of the select distinct queries.
This is kind of a complicated question. I have three tables:
A PRODUCTS table
ProductID
ProductName
Product A
Edwardian Desk
Product B
Edwardian Lamp
And a GROUPS table
ProductGroup
ProductID
Group A
Product A
Group A
Product B
Group B
Product C
And a SALES table
Product ID
Sales
Product A
1000
Product B
500
And I need to show the total of Sales per Product Group.
This part I understand; I wrote the query:
SELECT Groups.ProductGroup, SUM(Sales) AS TotalSales
FROM Groups
JOIN Sales
ON Groups.ProductID=Sales.ProductID
GROUP BY Groups.ProductGroup
This is the part that confuses me though: for each group, I need to pull in one of the names of the products in the group. However, it does not matter which name is pulled. So the final data could show:
Group A, Edwardian Desk, 1500
or
Group A, Edwardian Lamp, 1500
How can I pull the name of the product into my query?
I am working in Microsoft SQL Server
There's a number of ways to bring in one of your product's names, a couple of options are to either use an aggregation with a correlated subquery or to to use an apply.
Note, I've used aliases for your table names - doing so is good practice and makes queries more compact and easier to read. Also - presumably this is a contrived example and not your actual tables - but generally it's not a good practice to have column names identical to the table name, so if Sales on table Sales represents a quantity, then just call it Quantity!
select g.ProductGroup,
(select Min(ProductName) from Products p where p.ProductId=g.ProductId) FirstProductAlphabetically,
Sum(s.Sales) as TotalSales
from Groups g
join Sales s on s.ProductID=g.ProductID
group by g.ProductGroup
select g.ProductGroup,
p.ProductName as FirstProductById,
Sum(s.Sales) as TotalSales
from Groups g
join Sales s on s.ProductID=g.ProductID
cross apply (
select top (1) p.ProductName
from Products p
where p.ProductId=g.ProductId
order by ProductId
)p
group by g.ProductGroup
You can add products to the JOIN and use an aggregation function:
SELECT g.ProductGroup, SUM(s.Sales) AS TotalSales,
MIN(p.ProductName)
FROM Groups g JOIN
Sales s
ON g.ProductID = s.ProductID JOIN
Products p
ON p.ProductID = s.ProductId
GROUP BY g.ProductGroup;
Note: I often add two columns, MIN() and MAX() to get two sample names.
I should add. Your sample data has ProductIds that are not in the Products. That suggests a problem with either the question (more likely) or the data model. If you actually have references to non-existent products, then use a LEFT JOIN to Products rather than an inner join.
In many-to-many table, how to find ID where all criteria are matched, but maybe one row matches one criterion and another row matches another criterion?
For example, let's say I have a table that maps shopping carts to products, and another table where the products are defined.
How can I find a shopping cart that has at least one one match for every criterion?
Criteria could be, for example, product.category like '%fruit%', product.category like '%vegetable%', etc.
Ultimately I want to get back a shopping cart ID (could be all of them, but in my specific case I am happy to get any matching ID) that has at least one of each match in it.
I am assuming a table named cart_per_product with fields cart,product, and a table named product with fields product,category.
select cart from cart_per_product c
where exists
(
select 1 from product p1 where p1.product=c.product and p1.category like N'%fruit%'
)
and exists
(
select 1 from product p2 where p2.product=c.product and p2.category like N'%vegetable%'
)
You can use ANY and ALL operators combined with outer joins. A simple sample on a M:N relation:
select p.name
from products p
where id_product = ALL -- all operator
( select pc.id_product
from categories c
left outer join product_category pc on pc.id_product = p.id_product and
pc.id_category = c.id_category
)
I think you can figure out the column names
select c.id
from cart c
join product p
on c.pID = p.ID
group by c.id
having count(distinct p.catID) = (select count(distinct p.catID) from product)
Generic approach that possibly isn't the most efficient:
with data as (
select *,
count(case when <match condition> then 1 end)
over (partition by cartid) as matches
from <cart inner join products ...>
)
select * from data
where matches > 0;
This query select a list with the name and price of the most expensive articles by supplier, incluiding the provider name.
The tables are just:
Supplier: Code(PK) - Name
Articles: Code (PK) - Name - Price - Supplier (FK)
And the query is:
SELECT A.NAME, A.PRICE, S.NAME FROM ARTICLES A, SUPPLIERS S
WHERE A.SUPPLIER = S.CODE
AND A.PRICE =
(
SELECT MAX(A.PRICE)
FROM ARTICLES A
WHERE A.SUPPLIER = S.CODE
)
Would you please help me understand the logic behind? Why does this give me the max price PER SUPPLIER?
Thank you!
You inner query is getting the maximum price for a subset of articles - those that match the supplier.code passed in from the outer query. So the inner query says, "give me the highest price for supplier X."
The outer query is filtering the joined list to only provide those records that have match on the results from the inner query - those that happen to equal the highest price. It will match multiple records in the outer list if more than one record equates to the highest price for the supplier.
I have an e-commerce website (using VirtueMart) and I sell products that consist child products. When a product is a parent, it doesn't have ParentID, while it's children refer to it. I know, not the best logic but I didn't create it.
My SQL is very basic and I believe I ask for something quite easy to achieve
Select products that have children.
Sort results by prices (ASC/DSC).
SELECT * FROM Products INNER JOIN Prices ON Products.ProductID = Prices.ProductID ORDER BY Products.Price [ASC/DSC]
Explanation:
SELECT - Select (Get/Retrieve)
* - ALL
FROM Products - Get them from a DB Table named "Products".
INNER JOIN Prices - Selects all rows from both tables as long as there is a match between the columns in both tables. Rather, JOIN DB Table "Products" with DB Table "Prices".
ON - Like WHERE, this defines which rows will be checked for matches.
Products.ProductID = Prices.ProductID - Your match criteria. Get the rows where "ProductID" exists in both DB Tables "Products" and "Prices".
ORDER BY Products.Price [ASC/DSC] - Sorting. Use ASC for Ascending, DSC for Descending.
This table design is subpar for a number of reasons. First, it appears that the value 0 is being used to indicate lack of a parent (as there's no 0 ID for products). Typically this will be a NULL value instead.
If it were a NULL value, the SQL statement to get everything without a parent would be as simple as this:
SELECT * FROM Products WHERE ParentID IS NULL
However, we can't do that. If we make the assumption that 0 = no parent, we can do this:
SELECT * FROM Products WHERE ParentID = 0
However, that's a dangerous assumption to make. Thus, the correct way to do this (given your schema above), would be to compare the two tables and ensure that the parentID exists as a ProductID:
SELECT a.*
FROM Products AS a
WHERE EXISTS (SELECT * FROM Products AS b WHERE a.ID = b.ParentID)
Next, to get the pricing, we have to join those two tables together on a common ID. As the Prices table seems to reference a ProductID, we can use that like so:
SELECT p.ProductID, p.ProductName, pr.Price
FROM Products AS p INNER JOIN Prices AS pr ON p.ProductID = pr.ProductID
WHERE EXISTS (SELECT * FROM Products AS b WHERE p.ID = b.ParentID)
ORDER BY pr.Price
That might be sufficient per the data you've shown, but usually that type of table structure indicates that it's possible to have more than one price associated with a product (we're unable to tell whether this is true based on the quick snapshot).
That should get you close... if you need something more, we'll need more detail.
use the below script if you are using ssms.
SELECT pd.ProductId,ProductName,Price
FROM product pd
LEFT JOIN price pr ON pd.ProductId=pr.ProductID
WHERE EXISTS (SELECT 1 FROM product pd1 WHERE pd.productID=pd1.ParentID)
ORDER BY pr.Price ASC
Note :neither of your parent product have price in price table. If you want the sum of price of their child product use the below script.
SELECT pd.ProductId,pd.ProductName,SUM(ISNULL(pr.Price,0)) SUM_ChildPrice
FROM product pd
LEFT JOIN product pd1 ON pd.productID=pd1.ParentID
LEFT JOIN price pr ON pd1.ProductId=pr.ProductID
GROUP BY pd.ProductId,pd.ProductName
ORDER BY pr.Price ASC
You will have to use self-join:
For example:
SELECT * FROM products parent
JOIN products children ON parent.id = children.parent_id
JOIN prices ON prices.product_id = children.id
ORDER BY prices.price
Because we are using JOIN it will filter out all entries that don't have any children.
I haven't tested it, I hope it would work.