I'm trying to make a DQL query (doctrine from symfony 2.2) with no success on these entities:
Lesson
Which has several LessonContent
Which are each linked to a User
I want to retrieve all the lessons of a user (should be pretty basic...).
SELECT l, lc FROM MyBundle:LessonContent lc
JOIN lc.lesson l JOIN lc.modifiedBy u
WHERE lc.creation=1 AND u.id = :userId
But this returns the LessonContent entities. If I select from Lesson, I can't JOIN the lessons (which is probably what I should be doing).
Can anyone help me?
The main table you query from is what doctrine gives you back as the main objects, so the following should work (assuming l.content points to the LessonContent association):
SELECT l, lc FROM MyBundle:Lesson l
JOIN l.content lc
JOIN lc.modifiedBy u
WHERE lc.creation=1 AND u.id = :userId
It turned out I needed to have a l.content*s* attribute in order to be able to select from lessons and then JOIN on the rest.
Entity:
/**
* #var ArrayCollection $contentHistory
* #ORM\OneToMany(targetEntity="AAA\CoreBundle\Entity\LessonContent", mappedBy="lesson", cascade={"persist", "remove"})
* #ORM\OrderBy({"lastModified" = "DESC"})
*/
private $contentHistory;
Query:
SELECT l FROM AAACoreBundle:Lesson l JOIN l.contentHistory lc JOIN lc.modifiedBy u WHERE lc.creation=1 AND u.id = :userId GROUP BY l
And with that it works like a charm!
Related
I am trying to fetch customer and owner data
customer
|cnumber |id |
|080204220 |32859471000|
|907501981|6029151000|
role
|id|type|
|32859471000|owner|
|6029151000|customer|
result set
id|number|owner number|type|
|32859471000|080204220 |080204220 | owner
|6029151000|907501981|080204220 |customer
query
select c.id,sub.cnumber,c.cnumber, r.roletype
from customer c
inner join role r on c.id = r.id
left outer join (select c.cnumber ,r.roletype,c.id
from customer c
INNER JOIN role r
ON c.id = r.id ) sub on sub.roletype='owner';
This query gives proper result, but left outer join with same tables may cause impact on performance, is there any other way to achieve this?
I would prefer you to go with this only.
select c.id,sub.cnumber,c.cnumber, r.roletype
from customer c
inner join role r on c.id = r.id
left outer join (select c.cnumber ,r.roletype,c.id
from customer c
INNER JOIN role r
ON c.id = r.id ) sub on sub.roletype='owner';
As far as I can get the logic, you need to display an "owner"-customer among all of the others.
Since there is only one owner in the example data, I'd do it using the "cross join" (cartesian join)
select c.id,sub.cnumber,c.cnumber, r.roletype
from customer c
inner join role r on c.id = r.id
cross join (select c.cnumber ,r.roletype,c.id
from customer c
INNER JOIN role r
ON c.id = r.id where r.roletype='owner') sub
select c.id,sub.cnumber,c.cnumber, r.roletype
from customer c
inner join role r on c.id = r.id
left outer join (select c.cnumber ,r.roletype,c.id
from customer c
INNER JOIN role r
ON c.id = r.id ) sub on sub.roletype='owner';
I realised its quite difficult to explain my problem with only words, so i'm going to use an example to describe what i am trying to do instead.
So for example:
#model Book
has_many: book_genres
has_many: genres, through: :book_genres
#model Genre
has_many: book_genres
has_many: books, through: :book_genres
So finding books that belong to one genre only would be relatively straightforward, such as:
#method in books model
def self.find_books(genre)
#g = Genre.where('name LIKE ?' , "#{genre}").take
#b = #g.books
#get all the books that are of that genre
end
So in rails console i can do Book.find_books("Fiction") and then i would get all the books that are of fiction genre.
But how can i find all the books that are both "Young Adult" and "Fiction" ? Or what if i would like to query for books that have 3 genres, such as "Young Adult", "Fiction" and "Romance" ?
I could do g = Genre.where(name: ["Young Adult", "Fiction", "Romance"]) but subsequent to that i cannot do g.books and get all the books that are related to this 3 genres.
I am actually quite bad with active record so im not even sure if theres a better way to query through Books directly instead of finding Genre then finding all books that are associated with it.
But what i cannot wrap my head around is how do i get all the books that have multiple (specific)genres?
UPDATE:
So the current answers provided Book.joins(:genres).where("genres.name" => ["Young Adult", "Fiction", "Romance"]) works, but the problem is it returns all books that has the genre of Young Adult OR Fiction OR Romance.
What query do i pass so that the books return has ALL 3 Genres and not only 1 or 2 out of the 3?
Matching any of the given genres
The following should work for both an Array and a String:
Book.joins(:genres).where("genres.name" => ["Young Adult", "Fiction", "Romance"])
Book.joins(:genres).where("genres.name" => "Young Adult")
In general, it's better to pass a Hash to where, rather than trying to write a SQL snippet yourself.
See the Rails Guides for more details:
http://guides.rubyonrails.org/active_record_querying.html#hash-conditions
http://guides.rubyonrails.org/active_record_querying.html#specifying-conditions-on-the-joined-tables
Matching all of the given genres with one query
A single query could be built and then passed to .find_by_query:
def self.in_genres(genres)
sql = genres.
map { |name| Book.joins(:genres).where("genres.name" => name) }.
map { |relation| "(#{relation.to_sql})" }.
join(" INTERSECT ")
find_by_sql(sql)
end
This means that calling Book.in_genres(["Young Adult", "Fiction", "Romance"]) will run a query that looks something like this:
(SELECT books.* FROM books INNER JOIN … WHERE genres.name = 'Young Adult')
INTERSECT
(SELECT books.* FROM books INNER JOIN … WHERE genres.name = 'Fiction')
INTERSECT
(SELECT books.* FROM books INNER JOIN … WHERE genres.name = 'Romance');
It has the upside of letting the database do the heavy lifting of combining the result sets.
The downside is that we're using raw SQL, so we can't chain this with other ActiveRecord methods, for example Books.order(:title).in_genres(["Young Adult", "Fiction"]) will ignore the ORDER BY clause we've tried to add.
We're also manipulating SQL queries as strings. It's possible we could avoid this using Arel, but the way Rails and Arel handle binding query values makes this pretty complicated.
Matching all of the given genres with multiple query
It's also possible to use multiple queries:
def self.in_genres(genres)
ids = genres.
map { |name| Book.joins(:genres).where("genres.name" => name) }.
map { |relation| relation.pluck(:id).to_set }.
inject(:intersection).to_a
where(id: ids)
end
This means that calling Book.in_genres(["Young Adult", "Fiction", "Romance"]) will run four queries that look something like this:
SELECT id FROM books INNER JOIN … WHERE genres.name = 'Young Adult';
SELECT id FROM books INNER JOIN … WHERE genres.name = 'Fiction';
SELECT id FROM books INNER JOIN … WHERE genres.name = 'Romance';
SELECT * FROM books WHERE id IN (1, 3, …);
The downside here is that for N genres, we're making N+1 queries. The upside is that this can be combined with other ActiveRecord methods; Books.order(:title).in_genres(["Young Adult", "Fiction"]) will do our genre filtering, and sort by title.
I didn't try this but I think it will work
Book.joins(:genres).where("genres.name IN (?)", ["Young Adult", "Fiction", "Romance"])
Here is how I would do it in SQL:
SELECT *
FROM books
WHERE id IN (
SELECT bg.book_id
FROM book_genres bg
INNER JOIN genres g
ON g.id = bg.genre_id
WHERE g.name LIKE 'Young Adult'
INTERSECT
SELECT bg.book_id
FROM book_genres bg
INNER JOIN genres g
ON g.id = bg.genre_id
WHERE g.name LIKE 'Fiction'
INTERSECT
...
)
The inner query will contain only books belonging to all the genres you ask about.
Here is how I'd do it in ActiveRecord:
# book.rb
def self.in_genres(genre_names)
subquery = genre_names.map{|n|
<<-EOQ
SELECT bg.book_id
FROM book_genres bg
INNER JOIN genres g
ON g.id = bg.genre_id
WHERE g.name LIKE ?
EOQ
}.join("\nINTERSECT\n")
where(<<-EOQ, *genre_names)
id IN (
#{subquery}
)
EOQ
end
Note that I am using ? to avoid sql injection vulnerabilities, which is a problem in the code you proposed in your question.
Another approach would be to use multiple EXISTS conditions with correlated sub-queries:
SELECT *
FROM books
WHERE EXISTS (SELECT 1
FROM book_genres bg
INNER JOIN genres g
ON g.id = bg.genre_id
WHERE g.name LIKE 'Young Adult'
AND bg.book_id = books.id)
AND EXISTS (SELECT 1
FROM book_genres bg
INNER JOIN genres g
ON g.id = bg.genre_id
WHERE g.name LIKE 'Fiction'
AND bg.book_id = books.id)
AND ...
You'd construct this query in ActiveRecord similarly to the first approach. I'm not sure which would be faster, so you could try both if you like.
Here is yet another way to do the SQL---possibly fastest:
SELECT *
FROM books
WHERE id IN (
SELECT bg.book_id
FROM book_genres bg
INNER JOIN genres g
ON g.id = bg.genre_id
WHERE (g.name LIKE 'Young Adult' OR g.name LIKE 'Fiction' OR ...)
GROUP BY bg.book_id
HAVING COUNT(DISTINCT bg.genre_id) >= 2 -- or 3, or whatever
)
I'm trying to understand why I don't receive any records on a ruby on rails app using postgresql. This is the SQL query that is being executed:
SELECT g.program_id, g.title,
COALESCE(COUNT(pr), 0) AS ac, g.default
FROM groups AS g
LEFT OUTER JOIN memberships AS m ON m.group_id = g.id
LEFT OUTER JOIN progresses AS pr ON m.id = pr.participant_id
AND (pr.status = 'completed')
WHERE g.program_id = ANY(#1)
GROUP BY g.id
ORDER BY g.program_id, g.position, g.id
My question is: what does the ANY(#1) means?
Please have pacience, as I'm a ruby/rails/postgresql newbie.
Thanks!
Update: added some aditional code. Plese don't ident the query below as it is already idented above.
class StatsComponents::CompletedActivitiesPerGroupStats
include StatsComponent::Interface
GROUP_ACTIVITIES = <<-SQL
g.program_id, g.title, COALESCE(COUNT(pr), 0) AS ac, g.default
FROM groups AS g
LEFT OUTER JOIN memberships AS m ON m.group_id = g.id
LEFT OUTER JOIN progresses AS pr ON m.id = pr.participant_id
AND (pr.status = 'completed')
WHERE g.program_id = ANY(#1)
GROUP BY g.id
ORDER BY g.program_id, g.position, g.id
SQL
def generate
...
It selects records where g.program_id has a value existing in the array returned by #1 request, which they set as a query parameter (for example SELECT...) somewhere further in the program.
You can equally use SOME(#1) here.
By the way strictly speaking, this isn't a sql query. While there is no sql.execute or something like that, it's just a multiline string assignment.
I want to produce the following sql using active record.
WHERE (column_name1, column_name1) IN (SELECT ....)
I don't know how to do this is active record.
I've tried these so far
where('column_name1, column_name2' => {})
where([:column_name1, :column_name2] => {})
This is the full query I'd like to create
SELECT a, Count(1)
FROM table
WHERE ( a, b ) IN (SELECT a,
Max(b)
FROM table
GROUP BY a)
GROUP BY a
HAVING Count(1) > 1)
I've already written a scope for the subquery
Thanks in advance.
WHERE (column_name1, column_name1) IN (SELECT ....) is not a valid construct in sql; so it can't be done in active record either.
The valid way of accomplishing the same in SQL would be:
WHERE column_name1 IN (select ....) OR column_name2 IN (select ...)
The same query can be used directly in the active record:
where("column_name1 IN (select ...) OR column_name2 IN (select...)")
Avoiding duplication:
selected_values = select ...
where("column_name IN ? OR column_name2 in ?", selected_values, selected_values)
So I decided to use an inner join to gain the same functionality. Here is my solution.
select(:column1, 'Count(1)').
joins("INNER JOIN (#{subquery.to_sql}) AS table2 ON
table1.column1=table2.column1
AND table1.column2=table2.column2")
I'm trying to make a Rails model scope based on the following query:
SELECT * FROM tableA a
INNER JOIN tableB b ON a.id = b.id
WHERE a.id = (SELECT MAX(id) FROM tableB WHERE field = a.field)
I want to join rows of tableA with only one of tableB rows (the max one).
Is it possible?
Thank you!
TableA
.joins(:tableB)
.where("a.id = (SELECT MAX(id) FROM tableB WHERE field = a.field)")
You'll need to have an association between the two tables if you want the joins method works