Counting number of files in a folder in mysql - mysql

Question

I have these tables
Create table series (
id_series Int NOT NULL AUTO_INCREMENT,
name_series Varchar(100) NOT NULL,
kcal Int NOT NULL DEFAULT 0,
type Varchar(20) NOT NULL,
id_user Int NOT NULL,
UNIQUE (name_excercise),
Primary Key (id_series)) ENGINE = MyISAM;
Create table excercise (
id_excercise Int NOT NULL AUTO_INCREMENT,
name_excercise Char(100) NOT NULL,
date Date NOT NULL,
start Time NOT NULL,
end Time NOT NULL,
km Double(10,2) NOT NULL,
id_series Int NOT NULL,
UNIQUE (id_excercise),
Primary Key (id_excercise)) ENGINE = MyISAM;
They are basically like folders. Series has a name of a series and inside, there are subsequent excercises. What I need is to return every series user has and the number of the excercises inside. But I am having trouble with it, since I am not passing any ID of a concrete series in which it could count all the excercises. Is it possible to print that with only a user id?
I basically have this:
"SELECT * FROM series WHERE id_user = $id_user"
but need to combine it with this:
"SELECT COUNT(*) FROM excercise WHERE id_series = $id_series"
without the need of id_series.

Answer 1

This is the query:
SELECT S.*, COUNT(E.id_excercise) AS NumOfExc
FROM series AS S
JOIN excercise AS E
ON S.id_series = E.id_series
WHERE S.id_user = '$id_user'
GROUP BY E.id_series
UNION
SELECT *, 0 AS NumOfExc
FROM series
WHERE id_user = '$id_user'
AND id_series NOT IN (
SELECT S.id_series AS id_series
FROM series AS S
JOIN excercise AS E
ON S.id_series = E.id_series
WHERE S.id_user = '$id_user'
GROUP BY E.id_series
)
The above query will show what you need.