How to get last N records with activerecord

Question

With  limit in query  I will get first N records  What is the easiest way to get last N records

User · Answer

we can use Model last 5  or Model limit 5  order id   desc  in rails 5 2

User · Answer

Let s say N   5 and your model is Message  you can do something like this   Message order id   asc  from Message all order id   desc  limit 5    messages    Look at the sql   SELECT  messages    FROM     SELECT   messages    FROM  messages   ORDER BY  messages   created at  DESC LIMIT 5   messages  ORDER BY  messages   created at  ASC   The key is the subselect  First we need to define what are the last messages we want and then we have to order them in ascending order

User · Answer

Let s say N   5 and your model is Message  you can do something like this   Message order id   asc  from Message all order id   desc  limit 5    messages    Look at the sql   SELECT  messages    FROM     SELECT   messages    FROM  messages   ORDER BY  messages   created at  DESC LIMIT 5   messages  ORDER BY  messages   created at  ASC   The key is the subselect  First we need to define what are the last messages we want and then we have to order them in ascending order

User · Answer

This is the Rails 3 way  SomeModel last 5    last 5 records in ascending order  SomeModel last 5  reverse   last 5 records in descending order

User · Answer

For Rails 5  and likely Rails 4   Bad   Something last 5    because   Something last 5  class   gt  Array   so   Something last 50000  count   will likely blow up your memory or take forever   Good approach   Something limit 5  order  id desc     because   Something limit 5  order  id desc   class   gt  Image  ActiveRecord Relation  Something limit 5  order  id desc   to sql   gt   SELECT    somethings     FROM   somethings   ORDER BY id desc LIMIT 5    The latter is an unevaluated scope  You can chain it  or convert it to an array via  to a  So   Something limit 50000  order  id desc   count       takes a second

User · Answer

Add an  order parameter to the query

User · Answer

I find that this query is better faster for using the  pluck  method  which I love   Challenge limit 5  order  id desc     This gives an ActiveRecord as the output  so you can use  pluck on it like this   Challenge limit 5  order  id desc   pluck  id    which quickly gives the ids as an array while using optimal SQL code

User · Answer

Just try   Model order  field for sort desc   limit 5

User · Answer

If you have a default scope in your model that specifies an ascending order in Rails 3 you ll need to use reorder rather than order as specified by Arthur Neves above   Something limit 5  reorder  id desc     or   Something reorder  id desc   limit 5

User · Answer

Updated Answer  2020  You can get last N records simply by using last method  Record last N  Example  User last 5  Returns 5 users in descending order by their id  Deprecated  Old Answer  An active record query like this I think would get you what you want   Something  is the model name   Something find  all   order   gt   quot id desc quot    limit   gt  5  reverse  edit  As noted in the comments  another way  result   Something find  all   order   gt   quot id desc quot    limit   gt  5   while  result empty          puts result pop end

User · Answer

Solution is here   SomeModel last 5  reverse   Since rails is lazy  it will eventually hit the database with SQL like   SELECT  table   FROM table  ORDER BY table id DESC LIMIT 5

User · Answer

Updated Answer  2020  You can get last N records simply by using last method  Record last N  Example  User last 5  Returns 5 users in descending order by their id  Deprecated  Old Answer  An active record query like this I think would get you what you want   Something  is the model name   Something find  all   order   gt   quot id desc quot    limit   gt  5  reverse  edit  As noted in the comments  another way  result   Something find  all   order   gt   quot id desc quot    limit   gt  5   while  result empty          puts result pop end

User · Answer

new way to do it in rails 3 1 is SomeModel limit 5  order  id desc

User · Answer

Solution is here   SomeModel last 5  reverse   Since rails is lazy  it will eventually hit the database with SQL like   SELECT  table   FROM table  ORDER BY table id DESC LIMIT 5

User · Answer

Just try   Model order  field for sort desc   limit 5

User · Answer

If you need to set some ordering on results then use   Model order  name desc   limit n    n  number   if you do not need any ordering  and just need records saved in the table then use   Model last n    n  any number

User · Answer

Add an  order parameter to the query

User · Answer

Add an  order parameter to the query

User · Answer

Updated Answer  2020  You can get last N records simply by using last method  Record last N  Example  User last 5  Returns 5 users in descending order by their id  Deprecated  Old Answer  An active record query like this I think would get you what you want   Something  is the model name   Something find  all   order   gt   quot id desc quot    limit   gt  5  reverse  edit  As noted in the comments  another way  result   Something find  all   order   gt   quot id desc quot    limit   gt  5   while  result empty          puts result pop end

User · Answer

This is the Rails 3 way  SomeModel last 5    last 5 records in ascending order  SomeModel last 5  reverse   last 5 records in descending order

User · Answer

For Rails 4 and above version    You can try something like this If you want first oldest entry  YourModel order id   asc  limit 5  each do  d      You can try something like this if you want last latest entries    YourModel order id   desc  limit 5  each do  d

User · Answer

new way to do it in rails 3 1 is SomeModel limit 5  order  id desc

User · Answer

In my rails  rails 4 2  project  I use  Model last 10    get the last 10 record order by id   and it works

User · Answer

If you have a default scope in your model that specifies an ascending order in Rails 3 you ll need to use reorder rather than order as specified by Arthur Neves above   Something limit 5  reorder  id desc     or   Something reorder  id desc   limit 5

User · Answer

For Rails 5  and likely Rails 4   Bad   Something last 5    because   Something last 5  class   gt  Array   so   Something last 50000  count   will likely blow up your memory or take forever   Good approach   Something limit 5  order  id desc     because   Something limit 5  order  id desc   class   gt  Image  ActiveRecord Relation  Something limit 5  order  id desc   to sql   gt   SELECT    somethings     FROM   somethings   ORDER BY id desc LIMIT 5    The latter is an unevaluated scope  You can chain it  or convert it to an array via  to a  So   Something limit 50000  order  id desc   count       takes a second

User · Answer

we can use Model last 5  or Model limit 5  order id   desc  in rails 5 2

User · Answer

If you need to set some ordering on results then use   Model order  name desc   limit n    n  number   if you do not need any ordering  and just need records saved in the table then use   Model last n    n  any number

User · Answer

For Rails 4 and above version    You can try something like this If you want first oldest entry  YourModel order id   asc  limit 5  each do  d      You can try something like this if you want last latest entries    YourModel order id   desc  limit 5  each do  d

User · Answer

In my rails  rails 4 2  project  I use  Model last 10    get the last 10 record order by id   and it works

User · Answer

Updated Answer  2020  You can get last N records simply by using last method  Record last N  Example  User last 5  Returns 5 users in descending order by their id  Deprecated  Old Answer  An active record query like this I think would get you what you want   Something  is the model name   Something find  all   order   gt   quot id desc quot    limit   gt  5  reverse  edit  As noted in the comments  another way  result   Something find  all   order   gt   quot id desc quot    limit   gt  5   while  result empty          puts result pop end

User · Answer

I find that this query is better faster for using the  pluck  method  which I love   Challenge limit 5  order  id desc     This gives an ActiveRecord as the output  so you can use  pluck on it like this   Challenge limit 5  order  id desc   pluck  id    which quickly gives the ids as an array while using optimal SQL code

User · Answer

Add an  order parameter to the query

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