Order a table from values in another table - sql

Question

I have a table name 'Product'
ProductID ProductName
1 A
2 B
3 C
4 D
Another table named 'ViewedProduct'
ProductID Views UserID
2 2 55
2 1 40
1 10 40
1 50 127.0.1
3 51 127.0.1
for UserID 55 the expected result should be
ProductID ProductName
2 B
1 A
3 C
4 D
UserID 55 views should be at top and all other viewdproduct should come after it order by sum of their views. The product id 1 viewed by two different UserIDs thei total views is 60 that why it should come in second place. and product id 3 have 51 views it should come in third place.
Second Example :
ProductID Views UserID
2 2 55
3 3 55
2 1 40
1 10 40
1 50 127.0.1
3 51 127.0.1
4 50 127.0.1
Now for UserID 55 , it should first sort the result based on UserID 55. Then comes the rest result. Now the expected result i need should be
ProductID ProductName
3 C
2 B
1 A
4 D
Product ID 3 and 2 is not top because UserId 55 has viewed this 3 and 2 times respectively, the productid 1 is on the third place UserID 55 have not viewed this product. but their total views from viewed table is 60. And productID 4 comes last because userid 55 have not viewed this product but it total views from view table is 50. and so on..
-- Please comment if you need further explanation

Answer 1

I've edited the query to include the userID in the join clause as I believe this is necessary. see fiddle here: http://www.sqlfiddle.com/#!3/0ef18/1
SELECT
Product.ProductID,
Product.ProductName
FROM
Product
LEFT JOIN ViewedProduct ON Product.ProductID = ViewedProduct.ProductID AND ViewedProduct.UserID = #userID
WHERE
ViewedProduct.UserID IS NULL
OR ViewedProduct.UserID = #userID
ORDER BY
CASE WHEN ViewedProduct.Views IS NULL THEN 0 ELSE ViewedProduct.Views END DESC,
Product.ProductID
To order by the following:
UserViews,
AllViews,
ProductID
Use the following:
SELECT
Product.ProductID,
Product.ProductName
FROM
Product
LEFT JOIN ViewedProduct ON Product.ProductID = ViewedProduct.ProductID AND ViewedProduct.UserID = #userID
LEFT JOIN
(SELECT
ProductID,
SUM(Views) AllViews
FROM
ViewedProduct
GROUP BY
ProductID) TotalViewedProduct ON Product.ProductID = TotalViewedProduct.ProductID
ORDER BY
CASE WHEN ViewedProduct.Views IS NULL THEN 0 ELSE ViewedProduct.Views END DESC,
TotalViewedProduct.AllViews DESC,
Product.ProductID

Answer 2

It's not clear what you are asking here but if you want to return results from one of these tables and sort it by a column in another table just create a join between the main table and the table that holds the column you want to sort on. This will allow you to sort on columns in the joined table.
SELECT Product.ProductID, Product.ProductName
FROM Product
LEFT JOIN ViewedProduct ON Product.ProductID = ViewedProduct.ProductID
ORDER BY ViewedProduct.UserID
This however will not return the results you expect as UserID 55 has not viewed ProductID 1 or 3 and ordering will simply order ascending or descending.
If you want products viewed by UserID 55, you'll need a where clause:
SELECT Product.ProductID, Product.ProductName
FROM Product
LEFT JOIN ViewedProduct ON Product.ProductID = ViewedProduct.ProductID
WHERE ViewedProduct.UserID = 55
This will just return one row, unless there is more data than in your sample.
If you want to order by number of views try something like:
SELECT Product.ProductID, Product.ProductName
FROM Product
LEFT JOIN ViewedProduct ON Product.ProductID = ViewedProduct.ProductID
WHERE ViewedProduct.UserID = 55
ORDER BY ViewedProduct.Views