class Sequel::Dataset

A dataset represents an SQL query. Datasets can be used to select, insert, update and delete records.

Query results are always retrieved on demand, so a dataset can be kept around and reused indefinitely (datasets never cache results):

my_posts = DB[:posts].where(author: 'david') # no records are retrieved
my_posts.all # records are retrieved
my_posts.all # records are retrieved again

Datasets are frozen and use a functional style where modification methods return modified copies of the the dataset. This allows you to reuse datasets:

posts = DB[:posts]
davids_posts = posts.where(author: 'david')
old_posts = posts.where{stamp < Date.today - 7}
davids_old_posts = davids_posts.where{stamp < Date.today - 7}

Datasets are Enumerable objects, so they can be manipulated using many of the Enumerable methods, such as map and inject. Note that there are some methods that Dataset defines that override methods defined in Enumerable and result in different behavior, such as select and group_by.

For more information, see the “Dataset Basics” guide.