I have an issue with the below sub-query:
(select AVG(retail)
from STOCK
where category = 'TOYOTA' or category = 'HONDA') as AVERAGE_SALE_PRICE
Entire query:
select
d.name, s.category,(select AVG(retail)
where category = 'TOYOTA' or category = 'HONDA') as AVERAGE_SALE_PRICE
from dealer d join stock s using (dealerID)
The issue is that this calculated field returns the same value for all the rows in the query, I understand that I may have add a GROUP BY but I am quite confused where...
Thanks for any help
Try this query:
select AVG(retail) as AVERAGE_SALE_PRICE, category
from STOCK
where category='TOYOTA' or category='HONDA'
group by category
Update.This should give you the desired results:
select
d.name,
s.category,
(select AVG(s.retail)
from stock s1
where s1.dealerID = s.dealerID
and (s1.category = 'TOYOTA' or s1.category = 'HONDA') as AVERAGE_SALE_PRICE
from dealer d
join stock s using (dealerID)
Related
I have a recommendation system that uses SQL query similar to this one:
select B.* from user User1
join rating Rating1 on User1.user_id = Rating1.id and Rating1.value = 5
join product A on A.id = Rating1.product_id
join rating Rating2 on Rating2.product_id = A.id and Rating2.value = 5
join user User2 on User2.id = Rating2.user_id and User2.id <> User1.id
join rating RatingB on RatingB.user_id = User2.id and RatingB.value =5
join product B on B.id = RatingB.product_id
WHERE User1.id = 1;
This system recommends a product to a user if they didn’t buy that product yet. The recommendation is based on the rating of the product that they gave the best rating and it looks which other users also rated that product with the same rating.
How would this query look like in Cypher?
The mentioned SQL query would look something like this if it was written using Cypher:
MATCH (pA:PRODUCT)<-[r1:Rated {"rating":5}]-(n1:USER)-[r2:Rated {"rating":5}]->(pB:PRODUCT)
MATCH (n2:USER {id:1})-[r3:Rated {"rating":5}]->(pb)
WHERE n1.id != n2.id
RETURN pB;
How could I get this SQL query right in LINQ?
SQL query:
select c.Name, sum(t.value)
from Categories c
join Items i on c.Id = i.CategoryId
join Transactions t on t.ItemId = i.Id
where datepart(YEAR, t.CreatedTime) = 2016
and datepart(MONTH, t.CreatedTime) = 2
group by c.Name
I've tried to do the same in LINQ and got this:
var query = from cat in _context.Categories
join item in _context.Items on cat.Id equals item.CategoryId
join trans in _context.Transactions on item.Id equals trans.ItemId
where trans.CreatedTime.Month == e.RowIndex && trans.CreatedTime.Year == 2016
group new { cat.Name, trans.Value } by cat.Name into g
select new
{
Value = g.Sum(entry => entry.Value)
};
But it seems to be totally wrong, besides not giving me back the category names, it returns wrong values for the sums as well.
I have three tables:
Categories with columns Id and Name
Items with columns Id, Name, CategoryId, LastValue, IsIncome,
Transactions with columns Id, ItemId, Value, CreatedTime, IsIncome
I want to return all the values from my "Categories" table and join that to my "CategorySelections" table to display all the categories and whether the specified user selected them or not.
A complication (which I don't know how to deal with in LINQ) is that the user could have changed his selection/deselection of a particular category over time...each change would have logged in the "CategorySelections" table with a date stamp.
I am after the last selection status.
The following SQL query does what I want:
SELECT cs.UserId, c.CategoryId, m.MaxDate, cs.IsSelected
FROM [myDB].[dbo].[Categories] c
LEFT JOIN [myDB].[dbo].[CategorySelections] cs
ON c.CategoryID = cs.CategoryID AND cs.UserID = 7
INNER JOIN
(
SELECT UserId, CategoryId, Max(CreatedOn) as MaxDate
FROM [myDB].[dbo].[CategorySelections]
GROUP BY UserId, CategoryId
) m
ON cs.UserID = m.UserID AND cs.CategoryID = m.CategoryID AND cs.CreatedOn = m.MaxDate
ORDER BY cs.CategoryI
I need some help getting this done in LINQ.
Below is my attempt, which returns all the selections instead of just the last per category.
var query = from c in db.Category
join cs in db.CategorySelection.Where(x => x.UserID == WebSecurity.CurrentUserId)
on c.CategoryID equals cs.CategoryID into JoinedCategory
from cs in JoinedCategory.DefaultIfEmpty()
select new Selection() { CategoryID = c.CategoryID, CategoryName = c.CategoryName ,IsSelected = cs != null ? cs.IsSelected : false }
I am working in MVC; the "new Selection()" refers to my Model
You may add WHERE statement:
where cs.CreatedOn == CategorySelections.Where(t => t.CategoryId == cs.CategoryId).Max(r => r.CreatedOn)
I have a question about Linq select statement. I am new to Linq so any help will be very helpful. I did a lot of research but I still didn't manage to write down correct Linq statement.
I have this two tables and attributes:
Table Titles(title_id(PK), title) and
Table Sales(title_id(PK), qty)
where are title_id and title string values and qty is a number which represents some quantity.
I need to write a select which will take five most selling titles from this two tables.
So, I need to make sum from qty (we can have more records with the same Sales.title_id attribute) and make group by title_id and order by sum(qty) descending and then return attributes title and title_id.
How can I make suitable solution for my question?
Regards,
Dahakka
You can do group join of tables by title_id (each group g will represent all sales of joined title). Then select title description and total of sales for that title. Order result by totals, select title and take required number of top sales titles:
var query = (from t in db.Titles
join s in db.Sales on t.title_id equals s.title_id into g
select new { Title = t.title, Total = g.Sum(x => x.qty) } into ts
orderby ts.Total descending
select ts.Title).Take(5);
Resulting SQL will look like:
SELECT TOP (5) [t2].[title] AS [Title], [t2].[value] AS [Total]
FROM (
SELECT [t0].[title_id], (
SELECT SUM([t1].[qty])
FROM [Sales] AS [t1]
WHERE [t0].[title_id] = [t1].[title_id]
) AS [value]
FROM [Titles] AS [t0]
) AS [t2]
ORDER BY [t2].[value] DESC
Following is the linq query in method syntax
sales.GroupBy(s=>s.title_id)
.Select ( x =>
new {
Title_id = x.Key,
Sales= x.Sum (x=> x.qty)
})
.OrderByDescending(x=>x.Sales).Take(5)
.Join( titles,
sale=>sale.Title_id,
title=> title.title_id,
(sale, title)=> new
{
Title = title.Title,
TotalSales=sale.Sales
}
);
I'm having problems running a LINQ query between two tables and returning an answer set that doesen't match.
TB_AvailableProducts
-Prod_ID
-Name
....
TB_Purchases
-Cust_ID
-Prod_ID
Is there a way to get all distinct products that a customer has not purchased by using 1 LINQ query, or do I have to be doing two separate queries, 1 for all products and 1 for purchased products, and compare the two?
This query will return all products, which do not have related record in purchases table.
int customerID = 1;
var query = from ap in context.TB_AvailableProducts
join p in context.TB_Purchases.Where(x => x.Cust_ID == customerID)
on ap.Prod_ID equals p.Prod_ID into g
where !g.Any()
select ap;
I don't think you need Distinct here if you don't have duplicated records in your products table.
Generated SQL query will look like:
SELECT ap.Prod_ID, ap.Name
FROM TB_AvailableProducts AS ap
WHERE NOT EXISTS (SELECT
1 AS C1
FROM TB_Purchases AS p
WHERE (1 = p.Cust_ID) AND (ap.Prod_ID = p.Prod_ID)
)