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some corrections in the AR query guide [ci skip]

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Vijay Dev 2012-05-05 23:54:16 +05:30
parent ff1bcf6e45
commit a9668680fd
1 changed files with 15 additions and 13 deletions
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28
guides/source/active_record_querying.textile
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@ -101,7 +101,7 @@ SELECT * FROM clients WHERE (clients.id = 10) LIMIT 1
h5. +take+ h5. +take+
<tt>Model.take</tt> retrieves a record without any implicit ordering. The retrieved record may vary depending on the database engine. For example: <tt>Model.take</tt> retrieves a record without any implicit ordering. For example:
<ruby> <ruby>
client = Client.take client = Client.take
@ -114,11 +114,13 @@ The SQL equivalent of the above is:
SELECT * FROM clients LIMIT 1 SELECT * FROM clients LIMIT 1
</sql> </sql>
<tt>Model.take</tt> returns +nil+ if no record is found. No exception will be raised. <tt>Model.take</tt> returns +nil+ if no record is found and no exception will be raised.
TIP: The retrieved record may vary depending on the database engine.
h5. +first+ h5. +first+
<tt>Model.first</tt> finds the first record. If no order is chained it will order by primary key. For example: <tt>Model.first</tt> finds the first record ordered by the primary key. For example:
<ruby> <ruby>
client = Client.first client = Client.first
@ -131,11 +133,11 @@ The SQL equivalent of the above is:
SELECT * FROM clients ORDER BY clients.id ASC LIMIT 1 SELECT * FROM clients ORDER BY clients.id ASC LIMIT 1
</sql> </sql>
<tt>Model.first</tt> returns +nil+ if no matching record is found. No exception will be raised. <tt>Model.first</tt> returns +nil+ if no matching record is found and no exception will be raised.
h5. +last+ h5. +last+
<tt>Model.last</tt> finds the last record. If no order is chained it will order by primary key. For example: <tt>Model.last</tt> finds the last record ordered by the primary key. For example:
<ruby> <ruby>
client = Client.last client = Client.last
@ -148,7 +150,7 @@ The SQL equivalent of the above is:
SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1 SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1
</sql> </sql>
<tt>Model.last</tt> returns +nil+ if no matching record is found. No exception will be raised. <tt>Model.last</tt> returns +nil+ if no matching record is found and no exception will be raised.
h5. +find_by+ h5. +find_by+
@ -183,11 +185,11 @@ The SQL equivalent of the above is:
SELECT * FROM clients LIMIT 1 SELECT * FROM clients LIMIT 1
</sql> </sql>
<tt>Model.take!</tt> raises +RecordNotFound+ if no matching record is found. <tt>Model.take!</tt> raises +ActiveRecord::RecordNotFound+ if no matching record is found.
h5(#first_1). +first!+ h5(#first_1). +first!+
<tt>Model.first!</tt> finds the first record. If no order is chained it will order by primary key. For example: <tt>Model.first!</tt> finds the first record ordered by the primary key. For example:
<ruby> <ruby>
client = Client.first! client = Client.first!
@ -200,11 +202,11 @@ The SQL equivalent of the above is:
SELECT * FROM clients ORDER BY clients.id ASC LIMIT 1 SELECT * FROM clients ORDER BY clients.id ASC LIMIT 1
</sql> </sql>
<tt>Model.first!</tt> raises +RecordNotFound+ if no matching record is found. <tt>Model.first!</tt> raises +ActiveRecord::RecordNotFound+ if no matching record is found.
h5(#last_1). +last!+ h5(#last_1). +last!+
<tt>Model.last!</tt> finds the last record. If no order is chained it will order by primary key. For example: <tt>Model.last!</tt> finds the last record ordered by the primary key. For example:
<ruby> <ruby>
client = Client.last! client = Client.last!
@ -217,18 +219,18 @@ The SQL equivalent of the above is:
SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1 SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1
</sql> </sql>
<tt>Model.last!</tt> raises +RecordNotFound+ if no matching record is found. <tt>Model.last!</tt> raises +ActiveRecord::RecordNotFound+ if no matching record is found.
h5(#find_by_1). +find_by!+ h5(#find_by_1). +find_by!+
<tt>Model.find_by!</tt> finds the first record matching some conditions. It raises +RecordNotFound+ if no matching record is found. For example: <tt>Model.find_by!</tt> finds the first record matching some conditions. It raises +ActiveRecord::RecordNotFound+ if no matching record is found. For example:
<ruby> <ruby>
Client.find_by! first_name: 'Lifo' Client.find_by! first_name: 'Lifo'
# => #<Client id: 1, first_name: "Lifo"> # => #<Client id: 1, first_name: "Lifo">
Client.find_by! first_name: 'Jon' Client.find_by! first_name: 'Jon'
# => RecordNotFound # => ActiveRecord::RecordNotFound
</ruby> </ruby>
It is equivalent to writing: It is equivalent to writing: