Doctrine_manual-1-2-en

Chapter 10: Component Overview 176
Using Expression Values
There might be situations where you need to use SQL expressions as values of columns. This
can be achieved by using Doctrine_Expression which converts portable DQL expressions
to your native SQL expressions.
Lets say we have a class called event with columns timepoint(datetime) and
name(string). Saving the record with the current timestamp can be achieved as follows:
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// test.php
// ...
$user = new User();
$user->username = 'jwage';
$user->updated_at = new Doctrine_Expression('NOW()');
$user->save();
The above code would issue the following SQL query:
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INSERT INTO user (username, updated_at_) VALUES ('jwage', NOW())
When you use Doctrine_Expression with your objects in order to get the updated value
you will have to manually call refresh() to get the updated value from the database.
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// test.php
// ...
$user->refresh();
Getting Record State
Every Doctrine_Record has a state. First of all records can be transient or persistent.
Every record that is retrieved from database is persistent and every newly created record is
considered transient. If a Doctrine_Record is retrieved from database but the only loaded
property is its primary key, then this record has a state called proxy.
Every transient and persistent Doctrine_Record is either clean or dirty.
Doctrine_Record is clean when none of its properties are changed and dirty when at least
one of its properties has changed.
A record can also have a state called locked. In order to avoid infinite recursion in some rare
circular reference cases Doctrine uses this state internally to indicate that a record is
currently under a manipulation operation.
Below is a table containing all the different states a record can be in with a short description
of it:
Name
Doctrine_Record::STATE_PROXY
Description
Record is in proxy state meaning its persistent but
not all of its properties are loaded from the database.
Doctrine_Record::STATE_TCLEAN Record is transient clean, meaning its transient and
none of its properties are changed.
Doctrine_Record::STATE_TDIRTY Record is transient dirty, meaning its transient and
some of its properties are changed.
Doctrine_Record::STATE_DIRTY
Record is dirty, meaning its persistent and some of
its properties are changed.
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