Sum Two Columns in Two Mysql Tables

Question

I\'ve been searching everywhere for this but no cigar. Smoke is starting to come out of my ears. please help

How do you sum two columns in two tables and group by us

Answer 1

If you're selecting from 2 tables you need to join them. Otherwise MySQL will not know how to link up the two tables.

select sum(recipe_num_views + meal_num_views) 
from recipe r
inner join meals m ON (r.user_id = m.user_id)
group by m.user_id

See:
http://dev.mysql.com/doc/refman/5.5/en/join.html
http://www.codinghorror.com/blog/2007/10/a-visual-explanation-of-sql-joins.html

Answer 2

SELECT recipe.userid, sum(recipe_num_views+meal_num_views) 
FROM Recipe JOIN Meals ON recipe.userid=meals.userid
GROUP BY recipe.userid

EDIT:

OK, from your comments, I understand that when you have for user 3: 4 recipes & 3 meals you will get the sum of the combination of all these rows => sum(recipes)*3 + sum(meals)*4

Try this query instead:

select r.userid, (sum_recipe + sum_meal) sum_all
FROM
(select userid, sum(recipe_num_views) sum_recipe
FROM Recipe
GROUP BY userid) r
JOIN (
select userid, sum(meal_num_views) sum_meal
FROM Meals
GROUP BY userid) m ON r.userid = m.userid