Category: grouping

Rails has_many association count child rows

Post author By user user
Post date July 27, 2021
Categories In grouping, has-many, ruby-on-rails
6 Comments on Rails has_many association count child rows

What is the “rails way” to efficiently grab all rows of a parent table along with a count of the number of children each row has? I don’t want to use counter_cache as I want to run these counts based on some time conditions. The cliche blog example: Table of articles. Each article has 0 […]

Getting single records back from joined tables that may produce multiple records

Post author By user user
Post date July 18, 2021
Categories In group-by, grouping, select, sql, user-defined-functions
5 Comments on Getting single records back from joined tables that may produce multiple records

I’ve got a student table and an enrollment table; a student could have multiple enrollment records that can be active or inactive. I want to get a select that has a single student record and an indicator as to whether that student has active enrollments. I thought about doing this in an inline UDF that […]