I have the following table:
Book
| id | book_title |
|----|------------|
| 1 | a |
| 2 | b |
| 3 | c |
| 4 | d |
Teacher:
| id | teacher_name |
|----|--------------|
| 1 | a |
| 2 | b |
| 3 | c |
| 4 | d |
Education stage:
| id | education_stage_name |
|----|----------------------|
| 1 | a |
| 2 | b |
| 3 | c |
| 4 | d |
The relationship between book and education stage:
| book_id | education_stage_id |
|---------|--------------------|
| 1 | 1 |
| 1 | 2 |
| 2 | 3 |
| 3 | 4 |
And the relationship between book and teacher:
| book_id | teacher_id |
|---------|------------|
| 1 | 1 |
| 1 | 4 |
| 2 | 3 |
| 3 | 4 |
Now I want to select books, which has the same education stages as a teacher with id=1
So the result table should look like this:
| book_id | title |
|---------|-------|
| 1 | a |
Because only the education stage with id=1 is assigned to the book and the teacher with id=1 at the same time.
Here is the fiddle, but I don't know even how to start with this query.
Is there anyone that has some ideas on how to write this query?
Is it possible to write it with DQL language?
This doesn't take anything complex, if all records will always exist, you can inner join on all tables:
select
Book.id as book_id,
Book.book_title,
Teacher.id as teacher_id,
Teacher.teacher_name
from Book
inner join book_education_stage bes on bes.book_id = Book.id
inner join Education_Stage es on es.id = bes.education_stage_id
inner join teacher_education_stage tes on tes.book_id = Book.id
inner join Teacher on tes.teacher_id = Teacher.id
Result:
book_id
book_title
teacher_id
teacher_name
1
a
1
a
1
a
1
a
1
a
4
d
1
a
4
d
2
b
3
c
3
c
4
d
Here is the DB Fiddle if you're interested.
Related
I need a help with mySQL SELECT query from multiple tables. I have got four tables: school, discipline, pupils and teams.
School table looks like:
+------+---------+---------------+----------+
| id | name | discipline_id | pupil_id |
+------+---------+---------------+----------+
| 1 | one | 2 | 5 |
+------+---------+---------------+----------+
| 2 | two | 3 | 8 |
+------+---------+---------------+----------+
| 3 | three | 4 | 12 |
+------+---------+---------------+----------+
Discipline table looks like:
+------+---------+
| id | name |
+------+---------+
| 1 | math |
+------+---------+
| 2 | bio |
+------+---------+
| 3 | liter |
+------+---------+
| 4 | geo |
+------+---------+
Teams table looks like:
+------+---------+---------------+-----------+
| id | name | school_id | member_id |
+------+---------+---------------+-----------+
| 1 | T1 | 1 | 3 |
+------+---------+---------------+-----------+
| 2 | T2 | 3 | 3 |
+------+---------+---------------+-----------+
| 3 | T3 | 2 | 9 |
+------+---------+---------------+-----------+
The result of disciplines I need to get with a "SELECT from discipline..." query by "member_id = 3" is:
+-----------------+---------------+
| discipline_name | discipline_id |
+-----------------+---------------+
| bio | 2 |
+-----------------+---------------+
| geo | 4 |
+-----------------+---------------+
By matching member's school and then getting its discipline, if it makes sense...Is it possible to do with just one mySQL query?
Type of: member_id 3 => school_id 1,3 => discipline_id = show related disciplines names and ids which are 2, 4
Thank you very much...
Your goal is not clear or makes no sense to me.
But here is what you are literally asking for:
SELECT
s.discipline_id
d.name
FROM teams t
LEFT JOIN school s
ON s.id = t.school_id
LEFT JOIN discipline d
ON d.id = s.discipline_id
WHERE t.member_id = 3
I am trying to get the how many students are enrolled in a class. The above works if there ARE records.
However, if the there are no results a single "record" is returned where all fields are NULL except the students_count which returns zero
+---+------+------+----------------+----------------+
| | id | name | professor_name | students_count |
+---+------+------+----------------+----------------+
| 1 | null | null | null | 0 |
+---+------+------+----------------+----------------+
I would like for there to be NO records returned.
If a record returns it looks like this.
+---+----+-------------+----------------+----------------+
| | id | name | professor_name | students_count |
+---+----+-------------+----------------+----------------+
| 1 | 1 | Science 101 | Atkins | 16 |
+---+----+-------------+----------------+----------------+
I have tried variations on the LEFT JOIN and a combination of IFNULL(COUNT(DISTINCT students.id), null) AS students_count
But I can't seem to get it to work.
Any help?
SELECT classes.*,
professors.name AS professor_name,
COUNT(DISTINCT students.id) AS students_count
FROM classes
INNER JOIN professors ON classes.professor_id = professors.id
LEFT JOIN students ON classes.id = students.class_id AND classes.class_id IS NOT NULL
WHERE classes.class_id = 3
Using the generic data below, with class_id of 3, the result SHOULD be no records. But the null record with the count as 0 is returned.
+---+------+------+----------------+----------------+
| | id | name | professor_name | students_count |
+---+------+------+----------------+----------------+
| 1 | null | null | null | 0 |
+---+------+------+----------------+----------------+
Using the class_id of 1 will return:
+---+----+-------------+----------------+----------------+
| | id | name | professor_name | students_count |
+---+----+-------------+----------------+----------------+
| 1 | 1 | Science 101 | Atkins | 4 |
+---+----+-------------+----------------+----------------+
Generic Data
Classes
+---+-------------+---------------+
| | name | professors_id |
+---+-------------+---------------+
| 1 | Science 101 | 1 |
+---+-------------+---------------+
| 2 | Math | 2 |
+---+-------------+---------------+
| 3 | English | 3 |
+---+-------------+---------------+
Professors
+----+--------+
| id | name |
+----+--------+
| 1 | Atkins |
+----+--------+
| 2 | Button |
+----+--------+
| 3 | Castor |
+----+--------+
Students
+----+-------+------------+
| id | name | classes_id |
+----+-------+------------+
| 1 | Adam | 1 |
+----+-------+------------+
| 2 | Beth | 1 |
+----+-------+------------+
| 3 | Chris | 1 |
+----+-------+------------+
| 4 | David | 1 |
+----+-------+------------+
| 5 | Erma | 2 |
+----+-------+------------+
You can try to use INNER JOIN instead of OUTER JOIN, because of LEFT JOIN will base on classes table.
SELECT classes.*,
professors.name AS professor_name,
COUNT(DISTINCT students.id) AS students_count
FROM classes
INNER JOIN professors ON classes.professor_id = professors.id
INNER JOIN students ON classes.id = students.class_id
WHERE classes.class_id = 3
sqlfiddle
EDIT
HAVING clause is for aggregate function condition. but you use HAVING classes.class_id IS NOT NULL that can move to where
SELECT classes.*,
professors.name AS professor_name,
COUNT(DISTINCT students.id) AS students_count
FROM classes
INNER JOIN professors ON classes.professor_id = professors.id
LEFT JOIN students ON classes.id = students.class_id
WHERE classes.class_id = 3 AND classes.class_id IS NOT NULL
this is my first time posting here. I don't seem to find the answer to my problem.
So... I'm arranging a DB for a school project, a cookbook that only shows recipes that can be made with existing elements from the "shelf".
These ingredients have to have an exact ingredients match.
user:
+---------------+------+----------+----------+
| email | name | lastname | password |
+---------------+------+----------+----------+
| pal#mail.com | John | Potato | password |
| they#mail.com | Mary | Carrot | password |
+---------------+------+----------+----------+
shelf:
+---------+------------+---------------+
| shelfID | ingredient | user |
+---------+------------+---------------+
| 1 | 1 | pal#mail.com |
| 2 | 2 | pal#mail.com |
| 3 | 3 | pal#mail.com |
| 4 | 4 | pal#mail.com |
| 5 | 10 | they#mail.com |
| 6 | 12 | they#mail.com |
+---------+------------+---------------+
This is my recipe_ingredient relationship table
recipe_ingredient:
+--------+------------+
| recipe | ingredient |
+--------+------------+
| 1 | 1 |
| 1 | 2 |
| 1 | 4 |
| 1 | 10 |
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
| 2 | 4 |
| 3 | 2 |
| 3 | 3 |
| 3 | 15 |
+--------+------------+
I've tried this query:
SELECT
rec_ing.recipe, shf.ingredient, shf.user
FROM
recipes_ingredients AS rec_ing
INNER JOIN
shelf AS shf ON rec_ing.ingredient = shf.ingredient
INNER JOIN
users AS usr ON shf.user = usr.email
WHERE
usr.email = 'pal#mail.com'
that returns this table:
+--------+------------+--------------+
| recipe | ingredient | user |
+--------+------------+--------------+
| 1 | 1 | pal#mail.com |
| 1 | 2 | pal#mail.com |
| 1 | 4 | pal#mail.com |
| 2 | 1 | pal#mail.com |
| 2 | 2 | pal#mail.com |
| 2 | 3 | pal#mail.com |
| 2 | 4 | pal#mail.com |
| 3 | 2 | pal#mail.com |
| 3 | 3 | pal#mail.com |
+--------+------------+--------------+
Although it's true that the Recipe 1 contains ingredients from my shelf, it's also missing Ingredient 10
+--------+------------+
| recipe | ingredient |
+--------+------------+
| 1 | 1 |
| 1 | 2 |
| 1 | 4 |
| 1 | 10 |
| ... | ... |
+--------+------------+
I'm trying to only get this kind of result set.
+--------+------------+
| recipe | ingredient |
+--------+------------+
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
| 2 | 4 |
+--------+------------+
Because Recipe 2 contains all elements from my shelf
I have been going around all day with this problem ... What could be missing?
This is a bit tricky, because you need to aggregate your current query by recipe, but you also need the original query to get back the full records. Sadly, MySQL does not support common table exprrssions or other features which could give us a less verbose query.
SELECT
rec_ing.recipe,
shf.ingredient,
shf.user
FROM recipes_ingredients AS rec_ing
INNER JOIN shelf AS shf
ON rec_ing.ingredient = shf.ingredient
INNER JOIN users AS usr
ON shf.user = usr.email
INNER JOIN
(
SELECT rec_ing.recipe
FROM recipes_ingredients AS rec_ing
INNER JOIN shelf AS shf
ON rec_ing.ingredient = shf.ingredient
LEFT JOIN users AS usr
ON shf.user = usr.email
WHERE
usr.email = 'pal#mail.com'
GROUP BY rec_ing.recipe
HAVING COUNT(usr.email) = COUNT(*)
) t
ON rec_ing.recipe = t.recipe
WHERE
usr.email = 'pal#mail.com'
The basic strategy here is to just do one additional join to a subquery which identifies all recipes where every ingredient belongs to a given user. The critical part is the following:
HAVING COUNT(usr.email) = COUNT(*)
This checks that the total number of rows for a given recipe matches the number of rows which have been assigned to a given user.
I have 3 table
major table:
+----+------------+
| id | major |
+----+------------+
| 1 | Computer |
| 2 | Architect |
| 3 | Designer |
+----+------------+
classroom table:
+----+----------+-------+
| id | major_id | name |
+----+----------+-------+
| 1 | 1 | A |
| 2 | 1 | B |
| 3 | 1 | C |
| 4 | 2 | A |
| 5 | 2 | B |
| 6 | 3 | A |
+----+----------+-------+
and finally, student_classroom table
+----+------------+--------------+----------+
| id | student | classroom_id | status |
+----+------------+--------------+----------+
| 1 | John | 1 | Inactive |
| 2 | Defou | 2 | Active |
| 3 | John | 2 | Active |
| 4 | Alexa | 1 | Active |
| 5 | Nina | 1 | Active |
+----+------------+--------------+----------+
how can I use propel to build query below
select
a.id,
a.major,
b.number_of_student,
c.number_of_classroom
from major a
left join (
select
major.major_id,
count(student_classroom.id) as number_of_student
from major
left join classroom on classroom.major_id = major.id
left join student_classroom on student_classroom.classroom_id = classroom.id
where student_classroom.`status` = 'Active'
group by major_id
) b on b.major_id = a.major_id
left join (
select
major.major_id,
count(classroom.id) as number_of_classroom
from major
left join classroom on classroom.major_id = major.id
group by major_id
) c on c.major_id = a.major_id
Because I want the final result would be something like this, I spend hours trying to figure it out without success.
+----+------------+-------------------+---------------------+
| id | major | number_of_student | number_of_classroom |
+----+------------+-------------------+---------------------+
| 1 | Computer | 4 | 3 |
| 2 | Architect | 0 | 2 |
| 3 | Designer | 0 | 1 |
+----+------------+-------------------+---------------------+
Try this
select
m.id,
m.major,
count(distinct s.id) as number_of_student ,
count(distinct c.id) as number_of_classroom
from major m
left join classroom c on
(m.id = c.major_id)
left join student_classroom s
on (s.classroom_id = c.id and c.major_id = m.id and s.status = 'active')
group by m.id
order by m.id
I have five mysql tables. shops
+----+--------------+--------------+
| id | name | address |
+----+--------------+--------------+
| 1 | Shop1 | Street1 |
| 2 | Shop2 | Street2 |
| 3 | Shop3 | Street3 |
| 4 | Shop4 | Street4 |
+----+--------------+--------------+
fruits
+----+--------------+--------------+
| id | fruit | price |
+----+--------------+--------------+
| 1 | Bannana | 2.5 |
| 2 | Apple | 2.1 |
| 3 | Orange | 1.8 |
| 4 | Plum | 2.2 |
+----+--------------+--------------+
availability
+----+--------------+--------------+
| id | shop_id | fruit_id |
+----+--------------+--------------+
| 1 | 1 | 2 |
| 2 | 2 | 2 |
| 3 | 1 | 3 |
| 4 | 2 | 1 |
+----+--------------+--------------+
shop_activity
+----+--------------+--------------+--------------+
| id | shop_id | user_id | status |
+----+--------------+--------------+--------------+
| 1 | 2 | 1 | 1 |
| 2 | 3 | 2 | 1 |
| 3 | 1 | 2 | 2 |
| 4 | 2 | 2 | 1 |
+----+--------------+--------------+--------------+
users
+----+--------------+
| id | name |
+----+--------------+
| 1 | Peter |
| 2 | John |
+----+--------------+
I have query
SELECT
availability.shop_id,
shops.name
FROM availability
LEFT JOIN shops
ON availability.shop_id=shops.id
WHERE
fruit_id = 2
As a result I get name list of shops where fruit with id 2 (apple) is available.
What should I do so that I can include shop_activity table in query to get user's status if users.id = 1 beside proper shop. Something like this...
Shop1, NULL
Shop2, status: 1
You could try something like this:
SELECT
availability.shop_id,
shops.name,
shop_activity.status
FROM availability
LEFT JOIN shops
ON availability.shop_id=shops.id
LEFT JOIN shop_activity
ON shop_activity.shop_id = availability.shop_id
and shop_activity.user_id = 1
WHERE
fruit_id = 2
SELECT
availability.shop_id,
shops.name
FROM shops
LEFT JOIN availability ON availability.shop_id=shops.id
LEFT JOIN shop_activity ON shop_activity .shop_id=shops.id
WHERE
fruit_id = 2
and users.id=1
try making shops as the first table in left join
Try the following:
SELECT shops.name, shop_activity.status
FROM shops
INNER JOIN availability ON availability.shop_id = shops.id
AND availability.fruit_id = 2
LEFT JOIN shop_activity ON shops.shop_id = shop_activity.shop_id
AND shop_activity.user_id = 1
This should give you a row for every shop with apples, but the status will show as null for shops where the user has no activity, otherwise shows the status of that user.