Question

I’m having problems getting an accurate count of a column after joining others. When a column is joined I would still like to have a DISTINCT count of the table that it is being joined on.

A restaurant has multiple meals, meals have multiple food groups, food groups have multiple ingredients.

Through the restaurants id I want to be able to calculate how many of meals, food groups, and ingrediants the restaurant has.

When I join the food_groups the count for meals increases as well (I understand this is natural behavior I just don’t understand how to get what I need due to it.) I have tried DISTINCT and other things I have found, but nothing seems to do the trick. I would like to keep this to one query rather than splitting it up into multiple ones.

SELECT 
    COUNT(meals.id) AS countMeals,
    COUNT(food_groups.id) AS countGroups,
    COUNT(ingrediants.id) AS countIngrediants
FROM 
    restaurants 
INNER JOIN 
    meals ON restaurants.id = meals.restaurant_id
INNER JOIN
    food_groups ON meals.id = food_groups.meal_id 
INNER JOIN
    ingrediants ON food_groups.id = ingrediants.food_group_id     
WHERE 
    restaurants.id='43'
GROUP BY
    restaurants.id

Thanks!

Answer 1

The DISTINCT goes inside the count

SELECT 
    COUNT(DISTINCT meals.id) AS countMeals,
    COUNT(DISTINCT food_groups.id) AS countGroups,
    COUNT(DISTINCT ingrediants.id) AS countIngrediants
FROM 
    restaurants 
INNER JOIN 
    meals ON restaurants.id = meals.restaurant_id
INNER JOIN
    food_groups ON meals.id = food_groups.meal_id 
INNER JOIN
    ingrediants ON food_groups.id = ingrediants.food_group_id     
WHERE 
    restaurants.id='43'
GROUP BY
    restaurants.id