Tag: Power Page 1 of 13

This article is only meant for major, major SQL geeks. You’ll be bored out of your mind if you’re not one; don’t tell me I didn’t warn you.

As you might have guessed, there’s one, only one query powering the basic cocktail builder functionality. It’s the query that answers the question “if I have ingredients A, B, and C, give me a list of all cocktails that I can make”. Also:

• give me cocktails that I can almost make, ordered by the number of missing ingredients (i.e. those that I can make right away go first, those that are missing a single ingredient second, etc).
• consider ingredient substitutions (a concept I refer to as “normalized ingredients”): if you have Sky Vodka, and the recipe calls for Stoli, you can make the cocktail just fine.
• calculate cocktail ratings from the user feedback

As you might guess, the SQL is rather involved. Here’s the statement that gets executed when the user has two ingredients – items with ID’s 73 and 76:

SELECT 

    InnerCountsTable.CocktailID, 

    InnerCountsTable.CocktailName, 

    InnerCountsTable.CocktailShortName,     

    CountPresent, 

    CountMissing, 

    FORMAT(round((AVG(rating.Rating)*2))/2, 1) AS Rating, 

    (CountPresent - CountMissing) as Difference 

FROM 

    (SELECT 

        cocktail.ID as CocktailID, 

        cocktail.Name as CocktailName, 

        cocktail.ShortName as CocktailShortName, 

        cocktail.Instructions as CocktailInstructions,

        SUM(IF(userHas.NormalizedIngredientID IS NULL, 1, 0)) 

            as CountMissing, 

        SUM(IF(userHas.NormalizedIngredientID IS NULL, 0, 1))

            as CountPresent 

        FROM 

            mix INNER JOIN ingredient 

                ON mix.IngredientID = ingredient.ID 

            LEFT JOIN (

                SELECT NormalizedIngredientID 

                FROM ingredient 

                WHERE ID=76 

                UNION 

                SELECT NormalizedIngredientID 

                FROM ingredient 

                WHERE ID=73) AS userHas 

                ON userHas.NormalizedIngredientID =

                    ingredient.NormalizedIngredientID 

            INNER JOIN cocktail ON mix.CocktailID = cocktail.ID 

            WHERE NOT (cocktail.Status = 'Cut') 

            GROUP BY mix.CocktailID) AS InnerCountsTable 

LEFT JOIN rating 

    ON InnerCountsTable.CocktailID = rating.CocktailID 

WHERE CountPresent > 0 

GROUP BY InnerCountsTable.CocktailID 

ORDER BY 

    CountMissing ASC, 

    Difference DESC, 

    CountPresent DESC LIMIT 30

A weird part of the query is the “UNION” part inside (the one that’s creating the userHas part). Basically, I don’t believe there’s any other way to create an in-memory virtual table in MySQL to do a JOIN with. Anyone got better ideas?

Or, maybe you can offer a completely different approach that will work faster?

Cocktail Builder: JavaScript Alcoholic