Store a single sql server row in variable and then use the column values to construct a query

Question

I have a problem where the user has set his preferences in a table.

The table has more than 5 columns. Now I want to search the other view with condition values that are in the preference table.

Example:

The Preference table has price range, colour etc

So I need to search the products with price and colours.

Now I want to do it in SQL Server itself i.e. passing the preference id, it will always return a single row and then from the columns get the values like min price, max price and then create a search query.

The Issue is I dont know that how I can store the preference row column values in variables so that I can use it.

I am using Entity Framework so that I cannot using Dynamic SQL too.

I only want to know the way by which I can store the column values of preference table.

• I only know that i can do it something like:

  @colour = Select Top 1 Colour from preferences;
  

But like this I need to write this query for every variable. Is there is some better way with something called as CTE etc.

Answer 1

You have to declare the variables, then you can use them to assign the values in the SELECT and use them later:

-- declare the variables
DECLARE @min_price decimal(8,2)
DECLARE @max_price decimal(8,2)
DECLARE @color varchar(20)

-- assign the values into the variables
SELECT 
    @min_price = MIN_PRICE
  , @max_price = MAX_PRICE
  , @color = Colour
FROM Preference
WHERE preference_id = (parameter of prefrence id)

-- Now you get all 3 values of Colour, Min Price, Max Price,
-- then these 3 values can be used for your query

SELECT *
FROM products 
WHERE colour = @color 
    AND price BETWEEN min_price AND @max_price

Or you can make a single query if these 3 variables are not used elsewhere:

SELECT *
FROM products p
INNER JOIN
(
  SELECT Colour, MIN_PRICE, MAX_PRICE
  FROM Preference
  WHERE preference_id = (parameter of prefrence id)
) pre ON (p.colour = pre.Colour AND p.price BETWEEN pre.MIN_PRICE AND pre.MAX_PRICE)