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https://github.com/silverstripe/silverstripe-framework
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@ -59,6 +59,48 @@ The relationship can also be navigated in [templates](../templates).
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<% end_if %>
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<% end_with %>
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## Polymorphic has_one
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A has_one can also be polymorphic, which allows any type of object to be associated.
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This is useful where there could be many use cases for a particular data structure.
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An additional column is created called "`<relationship-name>`Class", which along
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with the ID column identifies the object.
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To specify that a has_one relation is polymorphic set the type to 'DataObject'.
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Ideally, the associated has_many (or belongs_to) should be specified with dot notation.
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::php
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class Player extends DataObject {
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private static $has_many = array(
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"Fans" => "Fan.FanOf"
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);
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}
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class Team extends DataObject {
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private static $has_many = array(
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"Fans" => "Fan.FanOf"
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);
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}
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// Type of object returned by $fan->FanOf() will vary
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class Fan extends DataObject {
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// Generates columns FanOfID and FanOfClass
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private static $has_one = array(
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"FanOf" => "DataObject"
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);
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}
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<div class="warning" markdown='1'>
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Note: The use of polymorphic relationships can affect query performance, especially
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on joins, and also increases the complexity of the database and necessary user code.
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They should be used sparingly, and only where additional complexity would otherwise
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be necessary. E.g. Additional parent classes for each respective relationship, or
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duplication of code.
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</div>
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## has_many
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Defines 1-to-many joins. As you can see from the previous example, `$has_many` goes hand in hand with `$has_one`.
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@ -1,13 +1,22 @@
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title: SQLQuery
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summary: Write and modify direct database queries through SQLQuery.
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title: SQL Queries
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summary: Write and modify direct database queries through SQLExpression subclasses.
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# SQLQuery
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# SQLSelect
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A [api:SQLQuery] object represents a SQL query, which can be serialized into a SQL statement. Dealing with low-level
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SQL such as `mysql_query()` is not encouraged, since the ORM provides powerful abstraction API's.
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## Introduction
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For example, if you want to run a simple `COUNT` SQL statement, the following three statements are functionally
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equivalent:
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An object representing a SQL select query, which can be serialized into a SQL statement.
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It is easier to deal with object-wrappers than string-parsing a raw SQL-query.
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This object is used by the SilverStripe ORM internally.
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Dealing with low-level SQL is not encouraged, since the ORM provides
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powerful abstraction APIs (see [datamodel](/developer_guides/data_model_and_orm).
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Starting with SilverStripe 3, records in collections are lazy loaded,
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and these collections have the ability to run efficient SQL
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such as counts or returning a single column.
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For example, if you want to run a simple `COUNT` SQL statement,
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the following three statements are functionally equivalent:
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:::php
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// Through raw SQL.
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@ -20,95 +29,254 @@ equivalent:
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// Through the ORM.
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$count = Member::get()->count();
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If you do use raw SQL, you'll run the risk of breaking
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various assumptions the ORM and code based on it have:
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<div class="info">
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The SQLQuery object is used by the SilverStripe ORM internally. By understanding SQLQuery, you can modify the SQL that
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the ORM creates.
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* Custom getters/setters (object property can differ from database column)
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* DataObject hooks like onBeforeWrite() and onBeforeDelete()
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* Automatic casting
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* Default values set through objects
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* Database abstraction
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We'll explain some ways to use *SELECT* with the full power of SQL,
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but still maintain a connection to the ORM where possible.
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<div class="warning" markdown="1">
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Please read our [security topic](/developer_guides/security) to find out
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how to properly prepare user input and variables for use in queries
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</div>
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## Usage
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### Select
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### SELECT
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Selection can be done by creating an instance of `SQLSelect`, which allows
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management of all elements of a SQL SELECT query, including columns, joined tables,
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conditional filters, grouping, limiting, and sorting.
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E.g.
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:::php
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$sqlQuery = new SQLQuery();
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<?php
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$sqlQuery = new SQLSelect();
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$sqlQuery->setFrom('Player');
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$sqlQuery->selectField('FieldName', 'Name');
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$sqlQuery->selectField('YEAR("Birthday")', 'Birthyear');
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$sqlQuery->addLeftJoin('Team','"Player"."TeamID" = "Team"."ID"');
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$sqlQuery->addWhere('YEAR("Birthday") = 1982');
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$sqlQuery->addWhere(array('YEAR("Birthday") = ?' => 1982));
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// $sqlQuery->setOrderBy(...);
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// $sqlQuery->setGroupBy(...);
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// $sqlQuery->setHaving(...);
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// $sqlQuery->setLimit(...);
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// $sqlQuery->setDistinct(true);
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// Get the raw SQL (optional)
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$rawSQL = $sqlQuery->sql();
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// Get the raw SQL (optional) and parameters
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$rawSQL = $sqlQuery->sql($parameters);
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// Execute and return a Query object
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$result = $sqlQuery->execute();
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// Iterate over results
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foreach($result as $row) {
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echo $row['BirthYear'];
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echo $row['BirthYear'];
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}
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The `$result` is an array lightly wrapped in a database-specific subclass of `[api:Query]`. This class implements the
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*Iterator*-interface, and provides convenience-methods for accessing the data.
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The result of `SQLSelect::execute()` is an array lightly wrapped in a database-specific subclass of `[api:SS_Query]`.
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This class implements the *Iterator*-interface, and provides convenience-methods for accessing the data.
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### Delete
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### DELETE
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Deletion can be done either by calling `DB::query`/`DB::prepared_query` directly,
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by creating a `SQLDelete` object, or by transforming a `SQLQuery` into a `SQLDelete`
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object instead.
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For example, creating a `SQLDelete` object
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:::php
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$sqlQuery->setDelete(true);
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<?php
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### Insert / Update
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$query = SQLDelete::create()
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->setFrom('"SiteTree"')
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->setWhere(array('"SiteTree"."ShowInMenus"' => 0));
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$query->execute();
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<div class="alert" markdown="1">
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Currently not supported through the `SQLQuery` class, please use raw `DB::query()` calls instead.
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</div>
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Alternatively, turning an existing `SQLQuery` into a delete
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:::php
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DB::query('UPDATE "Player" SET "Status"=\'Active\'');
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<?php
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### Joins
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$query = SQLQuery::create()
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->setFrom('"SiteTree"')
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->setWhere(array('"SiteTree"."ShowInMenus"' => 0))
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->toDelete();
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$query->execute();
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Directly querying the database
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:::php
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<?php
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DB::prepared_query('DELETE FROM "SiteTree" WHERE "SiteTree"."ShowInMenus" = ?', array(0));
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### INSERT/UPDATE
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INSERT and UPDATE can be performed using the `SQLInsert` and `SQLUpdate` classes.
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These both have similar aspects in that they can modify content in
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the database, but each are different in the way in which they behave.
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Previously, similar operations could be performed by using the `DB::manipulate`
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function which would build the INSERT and UPDATE queries on the fly. This method
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still exists, but internally uses `SQLUpdate` / `SQLInsert`, although the actual
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query construction is now done by the `DBQueryBuilder` object.
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Each of these classes implements the interface `SQLWriteExpression`, noting that each
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accepts write key/value pairs in a number of similar ways. These include the following
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api methods:
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* `addAssignments` - Takes a list of assignments as an associative array of key -> value pairs,
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but also supports SQL expressions as values if necessary.
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* `setAssignments` - Replaces all existing assignments with the specified list
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* `getAssignments` - Returns all currently given assignments, as an associative array
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in the format `array('Column' => array('SQL' => array('parameters)))`
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* `assign` - Singular form of addAssignments, but only assigns a single column value.
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* `assignSQL` - Assigns a column the value of a specified SQL expression without parameters
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`assignSQL('Column', 'SQL)` is shorthand for `assign('Column', array('SQL' => array()))`
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SQLUpdate also includes the following api methods:
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* `clear` - Clears all assignments
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* `getTable` - Gets the table to update
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* `setTable` - Sets the table to update. This should be ANSI quoted.
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E.g. `$query->setTable('"SiteTree"');`
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SQLInsert also includes the following api methods:
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* `clear` - Clears all rows
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* `clearRow` - Clears all assignments on the current row
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* `addRow` - Adds another row of assignments, and sets the current row to the new row
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* `addRows` - Adds a number of arrays, each representing a list of assignment rows,
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and sets the current row to the last one.
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* `getColumns` - Gets the names of all distinct columns assigned
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* `getInto` - Gets the table to insert into
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* `setInto` - Sets the table to insert into. This should be ANSI quoted.
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E.g. `$query->setInto('"SiteTree"');`
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E.g.
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:::php
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<?php
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$update = SQLUpdate::create('"SiteTree"')->where(array('ID' => 3));
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// assigning a list of items
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$update->addAssignments(array(
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'"Title"' => 'Our Products',
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'"MenuTitle"' => 'Products'
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));
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// Assigning a single value
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$update->assign('"MenuTitle"', 'Products');
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// Assigning a value using parameterised expression
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$title = 'Products';
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$update->assign('"MenuTitle"', array(
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'CASE WHEN LENGTH("MenuTitle") > LENGTH(?) THEN "MenuTitle" ELSE ? END' =>
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array($title, $title)
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));
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// Assigning a value using a pure SQL expression
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$update->assignSQL('"Date"', 'NOW()');
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// Perform the update
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$update->execute();
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In addition to assigning values, the SQLInsert object also supports multi-row
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inserts. For database connectors and API that don't have multi-row insert support
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these are translated internally as multiple single row inserts.
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For example,
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:::php
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<?php
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$insert = SQLInsert::create('"SiteTree"');
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// Add multiple rows in a single call. Note that column names do not need
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// to be symmetric
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$insert->addRows(array(
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array('"Title"' => 'Home', '"Content"' => '<p>This is our home page</p>'),
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array('"Title"' => 'About Us', '"ClassName"' => 'AboutPage')
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));
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// Adjust an assignment on the last row
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$insert->assign('"Content"', '<p>This is about us</p>');
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// Add another row
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$insert->addRow(array('"Title"' => 'Contact Us'));
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$columns = $insert->getColumns();
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// $columns will be array('"Title"', '"Content"', '"ClassName"');
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$insert->execute();
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### Value Checks
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Raw SQL is handy for performance-optimized calls,
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e.g. when you want a single column rather than a full-blown object representation.
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Example: Get the count from a relationship.
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:::php
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$sqlQuery = new SQLQuery();
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$sqlQuery->setFrom('Player');
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$sqlQuery->addSelect('COUNT("Player"."ID")');
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$sqlQuery->addWhere('"Team"."ID" = 99');
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$sqlQuery->addWhere(array('"Team"."ID"' => 99));
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$sqlQuery->addLeftJoin('Team', '"Team"."ID" = "Player"."TeamID"');
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$count = $sqlQuery->execute()->value();
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Note that in the ORM, this call would be executed in an efficient manner as well:
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:::php
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$count = $myTeam->Players()->count();
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### Mapping
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Creates a map based on the first two columns of the query result.
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This can be useful for creating dropdowns.
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Example: Show player names with their birth year, but set their birth dates as values.
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:::php
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$sqlQuery = new SQLQuery();
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$sqlQuery = new SQLSelect();
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$sqlQuery->setFrom('Player');
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$sqlQuery->setSelect('ID');
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$sqlQuery->setSelect('Birthdate');
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$sqlQuery->selectField('CONCAT("Name", ' - ', YEAR("Birthdate")', 'NameWithBirthyear');
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$map = $sqlQuery->execute()->map();
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$field = new DropdownField('Birthdates', 'Birthdates', $map);
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echo $map;
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Note that going through SQLSelect is just necessary here
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because of the custom SQL value transformation (`YEAR()`).
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An alternative approach would be a custom getter in the object definition.
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// returns array(
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// 1 => "Foo - 1920",
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// 2 => "Bar - 1936"
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// );
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:::php
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class Player extends DataObject {
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private static $db = array(
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'Name' => 'Varchar',
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'Birthdate' => 'Date'
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);
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function getNameWithBirthyear() {
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return date('y', $this->Birthdate);
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}
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}
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$players = Player::get();
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$map = $players->map('Name', 'NameWithBirthyear');
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## Related Documentation
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## Related
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* [Introduction to the Data Model and ORM](data_model_and_orm)
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## API Documentation
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* [api:DataObject]
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* [api:SQLQuery]
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* [api:SQLSelect]
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* [api:DB]
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* [api:Query]
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* [api:Database]
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