module ActiveRecord::QueryMethods
Constants
- FROZEN_EMPTY_ARRAY
- FROZEN_EMPTY_HASH
- VALID_UNSCOPING_VALUES
Public Instance Methods
Returns a new relation, which is the logical intersection of this relation and the one passed as an argument.
The two relations must be structurally compatible: they must be scoping the same model, and they must differ only by where
(if no group
has been defined) or having
(if a group
is present).
Post.where(id: [1, 2]).and(Post.where(id: [2, 3])) # SELECT `posts`.* FROM `posts` WHERE `posts`.`id` IN (1, 2) AND `posts`.`id` IN (2, 3)
# File lib/active_record/relation/query_methods.rb, line 824 def and(other) if other.is_a?(Relation) spawn.and!(other) else raise ArgumentError, "You have passed #{other.class.name} object to #and. Pass an ActiveRecord::Relation object instead." end end
Adds an SQL comment to queries generated from this relation. For example:
User.annotate("selecting user names").select(:name) # SELECT "users"."name" FROM "users" /* selecting user names */ User.annotate("selecting", "user", "names").select(:name) # SELECT "users"."name" FROM "users" /* selecting */ /* user */ /* names */
The SQL block comment delimiters, “/*” and “*/”, will be added automatically.
# File lib/active_record/relation/query_methods.rb, line 1198 def annotate(*args) check_if_method_has_arguments!(__callee__, args) spawn.annotate!(*args) end
Sets attributes to be used when creating new records from a relation object.
users = User.where(name: 'Oscar') users.new.name # => 'Oscar' users = users.create_with(name: 'DHH') users.new.name # => 'DHH'
You can pass nil
to create_with
to reset attributes:
users = users.create_with(nil) users.new.name # => 'Oscar'
# File lib/active_record/relation/query_methods.rb, line 1017 def create_with(value) spawn.create_with!(value) end
Specifies whether the records should be unique or not. For example:
User.select(:name) # Might return two records with the same name User.select(:name).distinct # Returns 1 record per distinct name User.select(:name).distinct.distinct(false) # You can also remove the uniqueness
# File lib/active_record/relation/query_methods.rb, line 1081 def distinct(value = true) spawn.distinct!(value) end
Forces eager loading by performing a LEFT OUTER JOIN on args
:
User.eager_load(:posts) # SELECT "users"."id" AS t0_r0, "users"."name" AS t0_r1, ... # FROM "users" LEFT OUTER JOIN "posts" ON "posts"."user_id" = # "users"."id"
# File lib/active_record/relation/query_methods.rb, line 200 def eager_load(*args) check_if_method_has_arguments!(__callee__, args) spawn.eager_load!(*args) end
Excludes the specified record (or collection of records) from the resulting relation. For example:
Post.excluding(post) # SELECT "posts".* FROM "posts" WHERE "posts"."id" != 1 Post.excluding(post_one, post_two) # SELECT "posts".* FROM "posts" WHERE "posts"."id" NOT IN (1, 2)
This can also be called on associations. As with the above example, either a single record of collection thereof may be specified:
post = Post.find(1) comment = Comment.find(2) post.comments.excluding(comment) # SELECT "comments".* FROM "comments" WHERE "comments"."post_id" = 1 AND "comments"."id" != 2
This is short-hand for .where.not(id: post.id)
and .where.not(id: [post_one.id, post_two.id])
.
An ArgumentError
will be raised if either no records are specified, or if any of the records in the collection (if a collection is passed in) are not instances of the same model that the relation is scoping.
# File lib/active_record/relation/query_methods.rb, line 1240 def excluding(*records) records.flatten!(1) records.compact! unless records.all?(klass) raise ArgumentError, "You must only pass a single or collection of #{klass.name} objects to ##{__callee__}." end spawn.excluding!(records) end
Used to extend a scope with additional methods, either through a module or through a block provided.
The object returned is a relation, which can be further extended.
Using a module¶ ↑
module Pagination def page(number) # pagination code goes here end end scope = Model.all.extending(Pagination) scope.page(params[:page])
You can also pass a list of modules:
scope = Model.all.extending(Pagination, SomethingElse)
Using a block¶ ↑
scope = Model.all.extending do def page(number) # pagination code goes here end end scope.page(params[:page])
You can also use a block and a module list:
scope = Model.all.extending(Pagination) do def per_page(number) # pagination code goes here end end
# File lib/active_record/relation/query_methods.rb, line 1127 def extending(*modules, &block) if modules.any? || block spawn.extending!(*modules, &block) else self end end
Extracts a named association
from the relation. The named association is first preloaded, then the individual association records are collected from the relation. Like so:
account.memberships.extract_associated(:user) # => Returns collection of User records
This is short-hand for:
account.memberships.preload(:user).collect(&:user)
# File lib/active_record/relation/query_methods.rb, line 233 def extract_associated(association) preload(association).collect(&association) end
Specifies the table from which the records will be fetched. For example:
Topic.select('title').from('posts') # SELECT title FROM posts
Can accept other relation objects. For example:
Topic.select('title').from(Topic.approved) # SELECT title FROM (SELECT * FROM topics WHERE approved = 't') subquery
Passing a second argument (string or symbol), creates the alias for the SQL from clause. Otherwise the alias “subquery” is used:
Topic.select('a.title').from(Topic.approved, :a) # SELECT a.title FROM (SELECT * FROM topics WHERE approved = 't') a
It does not add multiple arguments to the SQL from clause. The last from
chained is the one used:
Topic.select('title').from(Topic.approved).from(Topic.inactive) # SELECT title FROM (SELECT topics.* FROM topics WHERE topics.active = 'f') subquery
For multiple arguments for the SQL from clause, you can pass a string with the exact elements in the SQL from list:
color = "red" Color .from("colors c, JSONB_ARRAY_ELEMENTS(colored_things) AS colorvalues(colorvalue)") .where("colorvalue->>'color' = ?", color) .select("c.*").to_a # SELECT c.* # FROM colors c, JSONB_ARRAY_ELEMENTS(colored_things) AS colorvalues(colorvalue) # WHERE (colorvalue->>'color' = 'red')
# File lib/active_record/relation/query_methods.rb, line 1062 def from(value, subquery_name = nil) spawn.from!(value, subquery_name) end
Allows to specify a group attribute:
User.group(:name) # SELECT "users".* FROM "users" GROUP BY name
Returns an array with distinct records based on the group
attribute:
User.select([:id, :name]) # => [#<User id: 1, name: "Oscar">, #<User id: 2, name: "Oscar">, #<User id: 3, name: "Foo">] User.group(:name) # => [#<User id: 3, name: "Foo", ...>, #<User id: 2, name: "Oscar", ...>] User.group('name AS grouped_name, age') # => [#<User id: 3, name: "Foo", age: 21, ...>, #<User id: 2, name: "Oscar", age: 21, ...>, #<User id: 5, name: "Foo", age: 23, ...>]
Passing in an array of attributes to group by is also supported.
User.select([:id, :first_name]).group(:id, :first_name).first(3) # => [#<User id: 1, first_name: "Bill">, #<User id: 2, first_name: "Earl">, #<User id: 3, first_name: "Beto">]
# File lib/active_record/relation/query_methods.rb, line 356 def group(*args) check_if_method_has_arguments!(__callee__, args) spawn.group!(*args) end
Allows to specify a HAVING clause. Note that you can’t use HAVING without also specifying a GROUP clause.
Order.having('SUM(price) > 30').group('user_id')
# File lib/active_record/relation/query_methods.rb, line 882 def having(opts, *rest) opts.blank? ? self : spawn.having!(opts, *rest) end
Allows to specify an order by a specific set of values. Depending on your adapter this will either use a CASE statement or a built-in function.
User.in_order_of(:id, [1, 5, 3]) # SELECT "users".* FROM "users" # ORDER BY FIELD("users"."id", 1, 5, 3) # WHERE "users"."id" IN (1, 5, 3)
# File lib/active_record/relation/query_methods.rb, line 440 def in_order_of(column, values) klass.disallow_raw_sql!([column], permit: connection.column_name_with_order_matcher) return spawn.none! if values.empty? references = column_references([column]) self.references_values |= references unless references.empty? values = values.map { |value| type_caster.type_cast_for_database(column, value) } arel_column = column.is_a?(Symbol) ? order_column(column.to_s) : column spawn .order!(connection.field_ordered_value(arel_column, values)) .where!(arel_column.in(values)) end
Specify relationships to be included in the result set. For example:
users = User.includes(:address) users.each do |user| user.address.city end
allows you to access the address
attribute of the User
model without firing an additional query. This will often result in a performance improvement over a simple join.
You can also specify multiple relationships, like this:
users = User.includes(:address, :friends)
Loading nested relationships is possible using a Hash:
users = User.includes(:address, friends: [:address, :followers])
conditions¶ ↑
If you want to add string conditions to your included models, you’ll have to explicitly reference them. For example:
User.includes(:posts).where('posts.name = ?', 'example')
Will throw an error, but this will work:
User.includes(:posts).where('posts.name = ?', 'example').references(:posts)
Note that includes
works with association names while references
needs the actual table name.
If you pass the conditions via hash, you don’t need to call references
explicitly, as where
references the tables for you. For example, this will work correctly:
User.includes(:posts).where(posts: { name: 'example' })
# File lib/active_record/relation/query_methods.rb, line 184 def includes(*args) check_if_method_has_arguments!(__callee__, args) spawn.includes!(*args) end
Allows you to invert an entire where clause instead of manually applying conditions.
class User scope :active, -> { where(accepted: true, locked: false) } end User.where(accepted: true) # WHERE `accepted` = 1 User.where(accepted: true).invert_where # WHERE `accepted` != 1 User.active # WHERE `accepted` = 1 AND `locked` = 0 User.active.invert_where # WHERE NOT (`accepted` = 1 AND `locked` = 0)
Be careful because this inverts all conditions before invert_where
call.
class User scope :active, -> { where(accepted: true, locked: false) } scope :inactive, -> { active.invert_where } # Do not attempt it end # It also inverts `where(role: 'admin')` unexpectedly. User.where(role: 'admin').inactive # WHERE NOT (`role` = 'admin' AND `accepted` = 1 AND `locked` = 0)
# File lib/active_record/relation/query_methods.rb, line 790 def invert_where spawn.invert_where! end
Performs JOINs on args
. The given symbol(s) should match the name of the association(s).
User.joins(:posts) # SELECT "users".* # FROM "users" # INNER JOIN "posts" ON "posts"."user_id" = "users"."id"
Multiple joins:
User.joins(:posts, :account) # SELECT "users".* # FROM "users" # INNER JOIN "posts" ON "posts"."user_id" = "users"."id" # INNER JOIN "accounts" ON "accounts"."id" = "users"."account_id"
Nested joins:
User.joins(posts: [:comments]) # SELECT "users".* # FROM "users" # INNER JOIN "posts" ON "posts"."user_id" = "users"."id" # INNER JOIN "comments" ON "comments"."post_id" = "posts"."id"
You can use strings in order to customize your joins:
User.joins("LEFT JOIN bookmarks ON bookmarks.bookmarkable_type = 'Post' AND bookmarks.user_id = users.id") # SELECT "users".* FROM "users" LEFT JOIN bookmarks ON bookmarks.bookmarkable_type = 'Post' AND bookmarks.user_id = users.id
# File lib/active_record/relation/query_methods.rb, line 579 def joins(*args) check_if_method_has_arguments!(__callee__, args) spawn.joins!(*args) end
Performs LEFT OUTER JOINs on args
:
User.left_outer_joins(:posts) => SELECT "users".* FROM "users" LEFT OUTER JOIN "posts" ON "posts"."user_id" = "users"."id"
# File lib/active_record/relation/query_methods.rb, line 594 def left_outer_joins(*args) check_if_method_has_arguments!(__callee__, args) spawn.left_outer_joins!(*args) end
Specifies a limit for the number of records to retrieve.
User.limit(10) # generated SQL has 'LIMIT 10' User.limit(10).limit(20) # generated SQL has 'LIMIT 20'
# File lib/active_record/relation/query_methods.rb, line 896 def limit(value) spawn.limit!(value) end
Specifies locking settings (default to true
). For more information on locking, please see ActiveRecord::Locking
.
# File lib/active_record/relation/query_methods.rb, line 923 def lock(locks = true) spawn.lock!(locks) end
Returns a chainable relation with zero records.
The returned relation implements the Null Object pattern. It is an object with defined null behavior and always returns an empty array of records without querying the database.
Any subsequent condition chained to the returned relation will continue generating an empty relation and will not fire any query to the database.
Used in cases where a method or scope could return zero records but the result needs to be chainable.
For example:
@posts = current_user.visible_posts.where(name: params[:name]) # the visible_posts method is expected to return a chainable Relation def visible_posts case role when 'Country Manager' Post.where(country: country) when 'Reviewer' Post.published when 'Bad User' Post.none # It can't be chained if [] is returned. end end
# File lib/active_record/relation/query_methods.rb, line 966 def none spawn.none! end
Specifies the number of rows to skip before returning rows.
User.offset(10) # generated SQL has "OFFSET 10"
Should be used with order.
User.offset(10).order("name ASC")
# File lib/active_record/relation/query_methods.rb, line 912 def offset(value) spawn.offset!(value) end
Specify optimizer hints to be used in the SELECT statement.
Example (for MySQL):
Topic.optimizer_hints("MAX_EXECUTION_TIME(50000)", "NO_INDEX_MERGE(topics)") # SELECT /*+ MAX_EXECUTION_TIME(50000) NO_INDEX_MERGE(topics) */ `topics`.* FROM `topics`
Example (for PostgreSQL with pg_hint_plan):
Topic.optimizer_hints("SeqScan(topics)", "Parallel(topics 8)") # SELECT /*+ SeqScan(topics) Parallel(topics 8) */ "topics".* FROM "topics"
# File lib/active_record/relation/query_methods.rb, line 1156 def optimizer_hints(*args) check_if_method_has_arguments!(__callee__, args) spawn.optimizer_hints!(*args) end
Returns a new relation, which is the logical union of this relation and the one passed as an argument.
The two relations must be structurally compatible: they must be scoping the same model, and they must differ only by where
(if no group
has been defined) or having
(if a group
is present).
Post.where("id = 1").or(Post.where("author_id = 3")) # SELECT `posts`.* FROM `posts` WHERE ((id = 1) OR (author_id = 3))
# File lib/active_record/relation/query_methods.rb, line 856 def or(other) if other.is_a?(Relation) spawn.or!(other) else raise ArgumentError, "You have passed #{other.class.name} object to #or. Pass an ActiveRecord::Relation object instead." end end
Applies an ORDER BY
clause to a query.
order
accepts arguments in one of several formats.
symbols¶ ↑
The symbol represents the name of the column you want to order the results by.
User.order(:name) # SELECT "users".* FROM "users" ORDER BY "users"."name" ASC
By default, the order is ascending. If you want descending order, you can map the column name symbol to :desc
.
User.order(email: :desc) # SELECT "users".* FROM "users" ORDER BY "users"."email" DESC
Multiple columns can be passed this way, and they will be applied in the order specified.
User.order(:name, email: :desc) # SELECT "users".* FROM "users" ORDER BY "users"."name" ASC, "users"."email" DESC
strings¶ ↑
Strings are passed directly to the database, allowing you to specify simple SQL expressions.
This could be a source of SQL injection, so only strings composed of plain column names and simple function(column_name)
expressions with optional ASC
/DESC
modifiers are allowed.
User.order('name') # SELECT "users".* FROM "users" ORDER BY name User.order('name DESC') # SELECT "users".* FROM "users" ORDER BY name DESC User.order('name DESC, email') # SELECT "users".* FROM "users" ORDER BY name DESC, email
Arel
¶ ↑
If you need to pass in complicated expressions that you have verified are safe for the database, you can use Arel
.
User.order(Arel.sql('end_date - start_date')) # SELECT "users".* FROM "users" ORDER BY end_date - start_date
Custom query syntax, like JSON columns for Postgres, is supported in this way.
User.order(Arel.sql("payload->>'kind'")) # SELECT "users".* FROM "users" ORDER BY payload->>'kind'
# File lib/active_record/relation/query_methods.rb, line 418 def order(*args) check_if_method_has_arguments!(__callee__, args) do sanitize_order_arguments(args) end spawn.order!(*args) end
Allows preloading of args
, in the same way that includes
does:
User.preload(:posts) # SELECT "posts".* FROM "posts" WHERE "posts"."user_id" IN (1, 2, 3)
# File lib/active_record/relation/query_methods.rb, line 214 def preload(*args) check_if_method_has_arguments!(__callee__, args) spawn.preload!(*args) end
Sets readonly attributes for the returned relation. If value is true (default), attempting to update a record will result in an error.
users = User.readonly users.first.save => ActiveRecord::ReadOnlyRecord: User is marked as readonly
# File lib/active_record/relation/query_methods.rb, line 980 def readonly(value = true) spawn.readonly!(value) end
Use to indicate that the given table_names
are referenced by an SQL string, and should therefore be JOINed in any query rather than loaded separately. This method only works in conjunction with includes
. See includes
for more details.
User.includes(:posts).where("posts.name = 'foo'") # Doesn't JOIN the posts table, resulting in an error. User.includes(:posts).where("posts.name = 'foo'").references(:posts) # Query now knows the string references posts, so adds a JOIN
# File lib/active_record/relation/query_methods.rb, line 247 def references(*table_names) check_if_method_has_arguments!(__callee__, table_names) spawn.references!(*table_names) end
Replaces any existing order defined on the relation with the specified order.
User.order('email DESC').reorder('id ASC') # generated SQL has 'ORDER BY id ASC'
Subsequent calls to order on the same relation will be appended. For example:
User.order('email DESC').reorder('id ASC').order('name ASC')
generates a query with ‘ORDER BY id ASC, name ASC’.
# File lib/active_record/relation/query_methods.rb, line 464 def reorder(*args) check_if_method_has_arguments!(__callee__, args) do sanitize_order_arguments(args) end spawn.reorder!(*args) end
Allows you to change a previously set select statement.
Post.select(:title, :body) # SELECT `posts`.`title`, `posts`.`body` FROM `posts` Post.select(:title, :body).reselect(:created_at) # SELECT `posts`.`created_at` FROM `posts`
This is short-hand for unscope(:select).select(fields)
. Note that we’re unscoping the entire select statement.
# File lib/active_record/relation/query_methods.rb, line 325 def reselect(*args) check_if_method_has_arguments!(__callee__, args) spawn.reselect!(*args) end
Reverse the existing order clause on the relation.
User.order('name ASC').reverse_order # generated SQL has 'ORDER BY name DESC'
# File lib/active_record/relation/query_methods.rb, line 1169 def reverse_order spawn.reverse_order! end
Allows you to change a previously set where condition for a given attribute, instead of appending to that condition.
Post.where(trashed: true).where(trashed: false) # WHERE `trashed` = 1 AND `trashed` = 0 Post.where(trashed: true).rewhere(trashed: false) # WHERE `trashed` = 0 Post.where(active: true).where(trashed: true).rewhere(trashed: false) # WHERE `active` = 1 AND `trashed` = 0
This is short-hand for unscope(where: conditions.keys).where(conditions)
. Note that unlike reorder, we’re only unscoping the named conditions – not the entire where statement.
# File lib/active_record/relation/query_methods.rb, line 752 def rewhere(conditions) scope = spawn where_clause = scope.build_where_clause(conditions) scope.unscope!(where: where_clause.extract_attributes) scope.where_clause += where_clause scope end
Works in two unique ways.
First: takes a block so it can be used just like Array#select
.
Model.all.select { |m| m.field == value }
This will build an array of objects from the database for the scope, converting them into an array and iterating through them using Array#select
.
Second: Modifies the SELECT statement for the query so that only certain fields are retrieved:
Model.select(:field) # => [#<Model id: nil, field: "value">]
Although in the above example it looks as though this method returns an array, it actually returns a relation object and can have other query methods appended to it, such as the other methods in ActiveRecord::QueryMethods
.
The argument to the method can also be an array of fields.
Model.select(:field, :other_field, :and_one_more) # => [#<Model id: nil, field: "value", other_field: "value", and_one_more: "value">]
You can also use one or more strings, which will be used unchanged as SELECT fields.
Model.select('field AS field_one', 'other_field AS field_two') # => [#<Model id: nil, field: "value", other_field: "value">]
If an alias was specified, it will be accessible from the resulting objects:
Model.select('field AS field_one').first.field_one # => "value"
Accessing attributes of an object that do not have fields retrieved by a select except id
will throw ActiveModel::MissingAttributeError:
Model.select(:field).first.other_field # => ActiveModel::MissingAttributeError: missing attribute: other_field
# File lib/active_record/relation/query_methods.rb, line 297 def select(*fields) if block_given? if fields.any? raise ArgumentError, "`select' with block doesn't take arguments." end return super() end check_if_method_has_arguments!(__callee__, fields, "Call `select' with at least one field.") spawn._select!(*fields) end
Sets the returned relation to strict_loading
mode. This will raise an error if the record tries to lazily load an association.
user = User.strict_loading.first user.comments.to_a => ActiveRecord::StrictLoadingViolationError
# File lib/active_record/relation/query_methods.rb, line 995 def strict_loading(value = true) spawn.strict_loading!(value) end
Checks whether the given relation is structurally compatible with this relation, to determine if it’s possible to use the and
and or
methods without raising an error. Structurally compatible is defined as: they must be scoping the same model, and they must differ only by where
(if no group
has been defined) or having
(if a group
is present).
Post.where("id = 1").structurally_compatible?(Post.where("author_id = 3")) # => true Post.joins(:comments).structurally_compatible?(Post.where("id = 1")) # => false
# File lib/active_record/relation/query_methods.rb, line 810 def structurally_compatible?(other) structurally_incompatible_values_for(other).empty? end
Deduplicate multiple values.
# File lib/active_record/relation/query_methods.rb, line 1210 def uniq!(name) if values = @values[name] values.uniq! if values.is_a?(Array) && !values.empty? end self end
Removes an unwanted relation that is already defined on a chain of relations. This is useful when passing around chains of relations and would like to modify the relations without reconstructing the entire chain.
User.order('email DESC').unscope(:order) == User.all
The method arguments are symbols which correspond to the names of the methods which should be unscoped. The valid arguments are given in VALID_UNSCOPING_VALUES
. The method can also be called with multiple arguments. For example:
User.order('email DESC').select('id').where(name: "John") .unscope(:order, :select, :where) == User.all
One can additionally pass a hash as an argument to unscope specific :where
values. This is done by passing a hash with a single key-value pair. The key should be :where
and the value should be the where value to unscope. For example:
User.where(name: "John", active: true).unscope(where: :name) == User.where(active: true)
This method is similar to except, but unlike except, it persists across merges:
User.order('email').merge(User.except(:order)) == User.order('email') User.order('email').merge(User.unscope(:order)) == User.all
This means it can be used in association definitions:
has_many :comments, -> { unscope(where: :trashed) }
# File lib/active_record/relation/query_methods.rb, line 517 def unscope(*args) check_if_method_has_arguments!(__callee__, args) spawn.unscope!(*args) end
Returns a new relation, which is the result of filtering the current relation according to the conditions in the arguments.
where
accepts conditions in one of several formats. In the examples below, the resulting SQL is given as an illustration; the actual query generated may be different depending on the database adapter.
string¶ ↑
A single string, without additional arguments, is passed to the query constructor as an SQL fragment, and used in the where clause of the query.
Client.where("orders_count = '2'") # SELECT * from clients where orders_count = '2';
Note that building your own string from user input may expose your application to injection attacks if not done properly. As an alternative, it is recommended to use one of the following methods.
array¶ ↑
If an array is passed, then the first element of the array is treated as a template, and the remaining elements are inserted into the template to generate the condition. Active Record takes care of building the query to avoid injection attacks, and will convert from the ruby type to the database type where needed. Elements are inserted into the string in the order in which they appear.
User.where(["name = ? and email = ?", "Joe", "joe@example.com"]) # SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com';
Alternatively, you can use named placeholders in the template, and pass a hash as the second element of the array. The names in the template are replaced with the corresponding values from the hash.
User.where(["name = :name and email = :email", { name: "Joe", email: "joe@example.com" }]) # SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com';
This can make for more readable code in complex queries.
Lastly, you can use sprintf-style % escapes in the template. This works slightly differently than the previous methods; you are responsible for ensuring that the values in the template are properly quoted. The values are passed to the connector for quoting, but the caller is responsible for ensuring they are enclosed in quotes in the resulting SQL. After quoting, the values are inserted using the same escapes as the Ruby core method Kernel::sprintf
.
User.where(["name = '%s' and email = '%s'", "Joe", "joe@example.com"]) # SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com';
If where
is called with multiple arguments, these are treated as if they were passed as the elements of a single array.
User.where("name = :name and email = :email", { name: "Joe", email: "joe@example.com" }) # SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com';
When using strings to specify conditions, you can use any operator available from the database. While this provides the most flexibility, you can also unintentionally introduce dependencies on the underlying database. If your code is intended for general consumption, test with multiple database backends.
hash¶ ↑
where
will also accept a hash condition, in which the keys are fields and the values are values to be searched for.
Fields can be symbols or strings. Values can be single values, arrays, or ranges.
User.where(name: "Joe", email: "joe@example.com") # SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com' User.where(name: ["Alice", "Bob"]) # SELECT * FROM users WHERE name IN ('Alice', 'Bob') User.where(created_at: (Time.now.midnight - 1.day)..Time.now.midnight) # SELECT * FROM users WHERE (created_at BETWEEN '2012-06-09 07:00:00.000000' AND '2012-06-10 07:00:00.000000')
In the case of a belongs_to relationship, an association key can be used to specify the model if an ActiveRecord
object is used as the value.
author = Author.find(1) # The following queries will be equivalent: Post.where(author: author) Post.where(author_id: author)
This also works with polymorphic belongs_to relationships:
treasure = Treasure.create(name: 'gold coins') treasure.price_estimates << PriceEstimate.create(price: 125) # The following queries will be equivalent: PriceEstimate.where(estimate_of: treasure) PriceEstimate.where(estimate_of_type: 'Treasure', estimate_of_id: treasure)
Joins¶ ↑
If the relation is the result of a join, you may create a condition which uses any of the tables in the join. For string and array conditions, use the table name in the condition.
User.joins(:posts).where("posts.created_at < ?", Time.now)
For hash conditions, you can either use the table name in the key, or use a sub-hash.
User.joins(:posts).where("posts.published" => true) User.joins(:posts).where(posts: { published: true })
no argument¶ ↑
If no argument is passed, where
returns a new instance of WhereChain
, that can be chained with not to return a new relation that negates the where clause.
User.where.not(name: "Jon") # SELECT * FROM users WHERE name != 'Jon'
See WhereChain
for more details on not.
blank condition¶ ↑
If the condition is any blank-ish object, then where
is a no-op and returns the current relation.
# File lib/active_record/relation/query_methods.rb, line 724 def where(*args) if args.empty? WhereChain.new(spawn) elsif args.length == 1 && args.first.blank? self else spawn.where!(*args) end end
Private Instance Methods
# File lib/active_record/relation/query_methods.rb, line 1499 def arel_column(field) field = klass.attribute_aliases[field] || field from = from_clause.name || from_clause.value if klass.columns_hash.key?(field) && (!from || table_name_matches?(from)) table[field] elsif field.match?(/\A\w+\.\w+\z/) table, column = field.split(".") predicate_builder.resolve_arel_attribute(table, column) do lookup_table_klass_from_join_dependencies(table) end else yield field end end
# File lib/active_record/relation/query_methods.rb, line 1482 def arel_columns(columns) columns.flat_map do |field| case field when Symbol arel_column(field.to_s) do |attr_name| connection.quote_table_name(attr_name) end when String arel_column(field, &:itself) when Proc field.call else field end end end
# File lib/active_record/relation/query_methods.rb, line 1330 def assert_mutability! raise ImmutableRelation if @loaded raise ImmutableRelation if defined?(@arel) && @arel end
# File lib/active_record/relation/query_methods.rb, line 1335 def build_arel(aliases = nil) arel = Arel::SelectManager.new(table) build_joins(arel.join_sources, aliases) arel.where(where_clause.ast) unless where_clause.empty? arel.having(having_clause.ast) unless having_clause.empty? arel.take(build_cast_value("LIMIT", connection.sanitize_limit(limit_value))) if limit_value arel.skip(build_cast_value("OFFSET", offset_value.to_i)) if offset_value arel.group(*arel_columns(group_values.uniq)) unless group_values.empty? build_order(arel) build_select(arel) arel.optimizer_hints(*optimizer_hints_values) unless optimizer_hints_values.empty? arel.distinct(distinct_value) arel.from(build_from) unless from_clause.empty? arel.lock(lock_value) if lock_value unless annotate_values.empty? annotates = annotate_values annotates = annotates.uniq if annotates.size > 1 arel.comment(*annotates) end arel end
# File lib/active_record/relation/query_methods.rb, line 1363 def build_cast_value(name, value) ActiveModel::Attribute.with_cast_value(name, value, Type.default_value) end
# File lib/active_record/relation/query_methods.rb, line 1367 def build_from opts = from_clause.value name = from_clause.name case opts when Relation if opts.eager_loading? opts = opts.send(:apply_join_dependency) end name ||= "subquery" opts.arel.as(name.to_s) else opts end end
# File lib/active_record/relation/query_methods.rb, line 1400 def build_join_buckets buckets = Hash.new { |h, k| h[k] = [] } unless left_outer_joins_values.empty? stashed_left_joins = [] left_joins = select_association_list(left_outer_joins_values, stashed_left_joins) do raise ArgumentError, "only Hash, Symbol and Array are allowed" end if joins_values.empty? buckets[:association_join] = left_joins buckets[:stashed_join] = stashed_left_joins return buckets, Arel::Nodes::OuterJoin else stashed_left_joins.unshift construct_join_dependency(left_joins, Arel::Nodes::OuterJoin) end end joins = joins_values.dup if joins.last.is_a?(ActiveRecord::Associations::JoinDependency) stashed_eager_load = joins.pop if joins.last.base_klass == klass end joins.each_with_index do |join, i| joins[i] = Arel::Nodes::StringJoin.new(Arel.sql(join.strip)) if join.is_a?(String) end while joins.first.is_a?(Arel::Nodes::Join) join_node = joins.shift if !join_node.is_a?(Arel::Nodes::LeadingJoin) && (stashed_eager_load || stashed_left_joins) buckets[:join_node] << join_node else buckets[:leading_join] << join_node end end buckets[:association_join] = select_association_list(joins, buckets[:stashed_join]) do |join| if join.is_a?(Arel::Nodes::Join) buckets[:join_node] << join else raise "unknown class: %s" % join.class.name end end buckets[:stashed_join].concat stashed_left_joins if stashed_left_joins buckets[:stashed_join] << stashed_eager_load if stashed_eager_load return buckets, Arel::Nodes::InnerJoin end
# File lib/active_record/relation/query_methods.rb, line 1319 def build_join_dependencies associations = joins_values | left_outer_joins_values associations |= eager_load_values unless eager_load_values.empty? associations |= includes_values unless includes_values.empty? join_dependencies = [] join_dependencies.unshift construct_join_dependency( select_association_list(associations, join_dependencies), nil ) end
# File lib/active_record/relation/query_methods.rb, line 1450 def build_joins(join_sources, aliases = nil) return join_sources if joins_values.empty? && left_outer_joins_values.empty? buckets, join_type = build_join_buckets association_joins = buckets[:association_join] stashed_joins = buckets[:stashed_join] leading_joins = buckets[:leading_join] join_nodes = buckets[:join_node] join_sources.concat(leading_joins) unless leading_joins.empty? unless association_joins.empty? && stashed_joins.empty? alias_tracker = alias_tracker(leading_joins + join_nodes, aliases) join_dependency = construct_join_dependency(association_joins, join_type) join_sources.concat(join_dependency.join_constraints(stashed_joins, alias_tracker, references_values)) end join_sources.concat(join_nodes) unless join_nodes.empty? join_sources end
# File lib/active_record/relation/query_methods.rb, line 1561 def build_order(arel) orders = order_values.compact_blank arel.order(*orders) unless orders.empty? end
# File lib/active_record/relation/query_methods.rb, line 1472 def build_select(arel) if select_values.any? arel.project(*arel_columns(select_values)) elsif klass.ignored_columns.any? || klass.enumerate_columns_in_select_statements arel.project(*klass.column_names.map { |field| table[field] }) else arel.project(table[Arel.star]) end end
Checks to make sure that the arguments are not blank. Note that if some blank-like object were initially passed into the query method, then this method will not raise an error.
Example:
Post.references() # raises an error Post.references([]) # does not raise an error
This particular method should be called with a method_name (__callee__) and the args passed into that method as an input. For example:
def references(*args)
check_if_method_has_arguments!(__callee__, args) ...
end
# File lib/active_record/relation/query_methods.rb, line 1681 def check_if_method_has_arguments!(method_name, args, message = nil) if args.blank? raise ArgumentError, message || "The method .#{method_name}() must contain arguments." else yield args if block_given? args.flatten! args.compact_blank! end end
# File lib/active_record/relation/query_methods.rb, line 1618 def column_references(order_args) references = order_args.flat_map do |arg| case arg when String, Symbol arg when Hash arg.keys end end references.map! { |arg| arg =~ /^\W?(\w+)\W?\./ && $1 }.compact! references end
# File lib/active_record/relation/query_methods.rb, line 1550 def does_not_support_reverse?(order) # Account for String subclasses like Arel::Nodes::SqlLiteral that # override methods like #count. order = String.new(order) unless order.instance_of?(String) # Uses SQL function with multiple arguments. (order.include?(",") && order.split(",").find { |section| section.count("(") != section.count(")") }) || # Uses "nulls first" like construction. /\bnulls\s+(?:first|last)\b/i.match?(order) end
# File lib/active_record/relation/query_methods.rb, line 1313 def each_join_dependencies(join_dependencies = build_join_dependencies, &block) join_dependencies.each do |join_dependency| join_dependency.each(&block) end end
# File lib/active_record/relation/query_methods.rb, line 1306 def lookup_table_klass_from_join_dependencies(table_name) each_join_dependencies do |join| return join.base_klass if table_name == join.table_name end nil end
# File lib/active_record/relation/query_methods.rb, line 1631 def order_column(field) arel_column(field) do |attr_name| if attr_name == "count" && !group_values.empty? table[attr_name] else Arel.sql(connection.quote_table_name(attr_name)) end end end
# File lib/active_record/relation/query_methods.rb, line 1581 def preprocess_order_args(order_args) @klass.disallow_raw_sql!( order_args.flat_map { |a| a.is_a?(Hash) ? a.keys : a }, permit: connection.column_name_with_order_matcher ) validate_order_args(order_args) references = column_references(order_args) self.references_values |= references unless references.empty? # if a symbol is given we prepend the quoted table name order_args.map! do |arg| case arg when Symbol order_column(arg.to_s).asc when Hash arg.map { |field, dir| case field when Arel::Nodes::SqlLiteral field.public_send(dir.downcase) else order_column(field.to_s).public_send(dir.downcase) end } else arg end end.flatten! end
# File lib/active_record/relation/query_methods.rb, line 1641 def resolve_arel_attributes(attrs) attrs.flat_map do |attr| case attr when Arel::Predications attr when Hash attr.flat_map do |table, columns| table = table.to_s Array(columns).map do |column| predicate_builder.resolve_arel_attribute(table, column) end end else attr = attr.to_s if attr.include?(".") table, column = attr.split(".", 2) predicate_builder.resolve_arel_attribute(table, column) else attr end end end end
# File lib/active_record/relation/query_methods.rb, line 1521 def reverse_sql_order(order_query) if order_query.empty? return [table[primary_key].desc] if primary_key raise IrreversibleOrderError, "Relation has no current order and table has no primary key to be used as default order" end order_query.flat_map do |o| case o when Arel::Attribute o.desc when Arel::Nodes::Ordering o.reverse when Arel::Nodes::NodeExpression o.desc when String if does_not_support_reverse?(o) raise IrreversibleOrderError, "Order #{o.inspect} cannot be reversed automatically" end o.split(",").map! do |s| s.strip! s.gsub!(/\sasc\Z/i, " DESC") || s.gsub!(/\sdesc\Z/i, " ASC") || (s << " DESC") end else o end end end
# File lib/active_record/relation/query_methods.rb, line 1612 def sanitize_order_arguments(order_args) order_args.map! do |arg| klass.sanitize_sql_for_order(arg) end end
# File lib/active_record/relation/query_methods.rb, line 1382 def select_association_list(associations, stashed_joins = nil) result = [] associations.each do |association| case association when Hash, Symbol, Array result << association when ActiveRecord::Associations::JoinDependency stashed_joins&.<< association else yield association if block_given? end end result end
# File lib/active_record/relation/query_methods.rb, line 1697 def structurally_incompatible_values_for(other) values = other.values STRUCTURAL_VALUE_METHODS.reject do |method| v1, v2 = @values[method], values[method] if v1.is_a?(Array) next true unless v2.is_a?(Array) v1 = v1.uniq v2 = v2.uniq end v1 == v2 end end
# File lib/active_record/relation/query_methods.rb, line 1515 def table_name_matches?(from) table_name = Regexp.escape(table.name) quoted_table_name = Regexp.escape(connection.quote_table_name(table.name)) /(?:\A|(?<!FROM)\s)(?:\b#{table_name}\b|#{quoted_table_name})(?!\.)/i.match?(from.to_s) end
# File lib/active_record/relation/query_methods.rb, line 1569 def validate_order_args(args) args.each do |arg| next unless arg.is_a?(Hash) arg.each do |_key, value| unless VALID_DIRECTIONS.include?(value) raise ArgumentError, "Direction \"#{value}\" is invalid. Valid directions are: #{VALID_DIRECTIONS.to_a.inspect}" end end end end