How to write this MySQL query using ActiveRecord
I'm working with a Rails 5 project and have a SQL query that looks like the following:
SELECT foo1.*
FROM foos foo1
WHERE foo1.created_at =
( SELECT MIN(foo2.created_at) FROM foos foo2 WHERE foo2.user_id = foo1.user_id );
The model here is named Foo and the underlying table is named foos. I want to write a method that'll basically give me one record per user_id with the earliest created_at timestamp which the SQL query above will solve. I just want to write it using ActiveRecord.
ruby-on-rails ruby-on-rails-5
asked Nov 23 '18 at 21:12
randombitsrandombits
11.6k58181351
add a comment |
I'm working with a Rails 5 project and have a SQL query that looks like the following:
SELECT foo1.*
FROM foos foo1
WHERE foo1.created_at =
( SELECT MIN(foo2.created_at) FROM foos foo2 WHERE foo2.user_id = foo1.user_id );
The model here is named Foo and the underlying table is named foos. I want to write a method that'll basically give me one record per user_id with the earliest created_at timestamp which the SQL query above will solve. I just want to write it using ActiveRecord.
ruby-on-rails ruby-on-rails-5
asked Nov 23 '18 at 21:12
randombitsrandombits
11.6k58181351
add a comment |
I'm working with a Rails 5 project and have a SQL query that looks like the following:
SELECT foo1.*
FROM foos foo1
WHERE foo1.created_at =
( SELECT MIN(foo2.created_at) FROM foos foo2 WHERE foo2.user_id = foo1.user_id );
The model here is named Foo and the underlying table is named foos. I want to write a method that'll basically give me one record per user_id with the earliest created_at timestamp which the SQL query above will solve. I just want to write it using ActiveRecord.
ruby-on-rails ruby-on-rails-5
asked Nov 23 '18 at 21:12
randombitsrandombits
11.6k58181351
I'm working with a Rails 5 project and have a SQL query that looks like the following:
SELECT foo1.*
FROM foos foo1
WHERE foo1.created_at =
( SELECT MIN(foo2.created_at) FROM foos foo2 WHERE foo2.user_id = foo1.user_id );
The model here is named Foo and the underlying table is named foos. I want to write a method that'll basically give me one record per user_id with the earliest created_at timestamp which the SQL query above will solve. I just want to write it using ActiveRecord.
ruby-on-rails ruby-on-rails-5
ruby-on-rails ruby-on-rails-5
asked Nov 23 '18 at 21:12
randombitsrandombits
11.6k58181351
asked Nov 23 '18 at 21:12
randombitsrandombits
11.6k58181351
asked Nov 23 '18 at 21:12
randombitsrandombits
11.6k58181351
asked Nov 23 '18 at 21:12
randombitsrandombits
11.6k58181351
asked Nov 23 '18 at 21:12
randombitsrandombits
11.6k58181351
11.6k58181351
add a comment |
add a comment |
1 Answer
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The initial query you have doesn't necessarily give you one record per user_id.
Here's an example:
# created_at1 < created_at2
foo1 = Foo.create!(user_id: 1, created_at: created_at1)
foo2 = Foo.create!(user_id: 1, created_at: created_at2)
foo3 = Foo.create!(user_id: 2, created_at: created_at2)
Your query will select the minimum created_at for each user_id, so it will get created_at1 from foo1 and created_at2 from foo3. But since foo2 and foo3 share the same created_at, all three records will be returned.
A better way to select the records would be (For Postgres):
Foo.select('DISTINCT ON ("user_id") *').order(:user_id, created_at: :asc)
answered Nov 23 '18 at 22:24
AbMAbM
5,19921423
add a comment |
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1 Answer
1
active
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1 Answer
1
active
oldest
votes
active
oldest
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active
oldest
votes
The initial query you have doesn't necessarily give you one record per user_id.
Here's an example:
# created_at1 < created_at2
foo1 = Foo.create!(user_id: 1, created_at: created_at1)
foo2 = Foo.create!(user_id: 1, created_at: created_at2)
foo3 = Foo.create!(user_id: 2, created_at: created_at2)
Your query will select the minimum created_at for each user_id, so it will get created_at1 from foo1 and created_at2 from foo3. But since foo2 and foo3 share the same created_at, all three records will be returned.
A better way to select the records would be (For Postgres):
Foo.select('DISTINCT ON ("user_id") *').order(:user_id, created_at: :asc)
answered Nov 23 '18 at 22:24
AbMAbM
5,19921423
add a comment |
The initial query you have doesn't necessarily give you one record per user_id.
Here's an example:
# created_at1 < created_at2
foo1 = Foo.create!(user_id: 1, created_at: created_at1)
foo2 = Foo.create!(user_id: 1, created_at: created_at2)
foo3 = Foo.create!(user_id: 2, created_at: created_at2)
Your query will select the minimum created_at for each user_id, so it will get created_at1 from foo1 and created_at2 from foo3. But since foo2 and foo3 share the same created_at, all three records will be returned.
A better way to select the records would be (For Postgres):
Foo.select('DISTINCT ON ("user_id") *').order(:user_id, created_at: :asc)
answered Nov 23 '18 at 22:24
AbMAbM
5,19921423
add a comment |
The initial query you have doesn't necessarily give you one record per user_id.
Here's an example:
# created_at1 < created_at2
foo1 = Foo.create!(user_id: 1, created_at: created_at1)
foo2 = Foo.create!(user_id: 1, created_at: created_at2)
foo3 = Foo.create!(user_id: 2, created_at: created_at2)
Your query will select the minimum created_at for each user_id, so it will get created_at1 from foo1 and created_at2 from foo3. But since foo2 and foo3 share the same created_at, all three records will be returned.
A better way to select the records would be (For Postgres):
Foo.select('DISTINCT ON ("user_id") *').order(:user_id, created_at: :asc)
answered Nov 23 '18 at 22:24
AbMAbM
5,19921423
The initial query you have doesn't necessarily give you one record per user_id.
Here's an example:
# created_at1 < created_at2
foo1 = Foo.create!(user_id: 1, created_at: created_at1)
foo2 = Foo.create!(user_id: 1, created_at: created_at2)
foo3 = Foo.create!(user_id: 2, created_at: created_at2)
Your query will select the minimum created_at for each user_id, so it will get created_at1 from foo1 and created_at2 from foo3. But since foo2 and foo3 share the same created_at, all three records will be returned.
A better way to select the records would be (For Postgres):
Foo.select('DISTINCT ON ("user_id") *').order(:user_id, created_at: :asc)
answered Nov 23 '18 at 22:24
AbMAbM
5,19921423
answered Nov 23 '18 at 22:24
AbMAbM
5,19921423
answered Nov 23 '18 at 22:24
AbMAbM
5,19921423
answered Nov 23 '18 at 22:24
AbMAbM
5,19921423
5,19921423
add a comment |
add a comment |
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