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Improve ActiveRecord::Querying documentation [ci skip]

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* Break up long sentences
* Reword some sentences to clarify subject, predicate, and object
* Explain drawbacks of using count_by_sql
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Aaron Sumner 2018-11-28 14:45:27 -08:00
parent a01e0d0fab
commit 96f6a59d8e
1 changed files with 9 additions and 7 deletions
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16
activerecord/lib/active_record/querying.rb
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@ -16,17 +16,17 @@ module ActiveRecord
delegate :pluck, :pick, :ids, to: :all delegate :pluck, :pick, :ids, to: :all
# Executes a custom SQL query against your database and returns all the results. The results will # Executes a custom SQL query against your database and returns all the results. The results will
# be returned as an array with columns requested encapsulated as attributes of the model you call # be returned as an array, with the requested columns encapsulated as attributes of the model you call
# this method from. If you call <tt>Product.find_by_sql</tt> then the results will be returned in # this method from. For example, if you call <tt>Product.find_by_sql</tt>, then the results will be returned in
# a +Product+ object with the attributes you specified in the SQL query. # a +Product+ object with the attributes you specified in the SQL query.
# #
# If you call a complicated SQL query which spans multiple tables the columns specified by the # If you call a complicated SQL query which spans multiple tables, the columns specified by the
# SELECT will be attributes of the model, whether or not they are columns of the corresponding # SELECT will be attributes of the model, whether or not they are columns of the corresponding
# table. # table.
# #
# The +sql+ parameter is a full SQL query as a string. It will be called as is, there will be # The +sql+ parameter is a full SQL query as a string. It will be called as is; there will be
# no database agnostic conversions performed. This should be a last resort because using, for example, # no database agnostic conversions performed. This should be a last resort because using
# MySQL specific terms will lock you to using that particular database engine or require you to # database-specific terms will lock you into using that particular database engine, or require you to
# change your call if you switch engines. # change your call if you switch engines.
# #
# # A simple SQL query spanning multiple tables # # A simple SQL query spanning multiple tables
@ -61,7 +61,9 @@ module ActiveRecord
# Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part. # Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part.
# The use of this method should be restricted to complicated SQL queries that can't be executed # The use of this method should be restricted to complicated SQL queries that can't be executed
# using the ActiveRecord::Calculations class methods. Look into those before using this. # using the ActiveRecord::Calculations class methods. Look into those before using this method,
# as it could lock you into a specific database engine or require a code change to switch
# database engines.
# #
# Product.count_by_sql "SELECT COUNT(*) FROM sales s, customers c WHERE s.customer_id = c.id" # Product.count_by_sql "SELECT COUNT(*) FROM sales s, customers c WHERE s.customer_id = c.id"
# # => 12 # # => 12