This section describes other methods of the Zend_Db_Select class
that are not covered above: getPart() and
reset().
The getPart() method returns a representation of one part
of your SQL query. For example, you can use this method to return
the array of expressions for the WHERE clause, or the array of
columns (or column expressions) that are in the SELECT list, or
the values of the count and offset for the LIMIT clause.
The return value is not a string containing a fragment of SQL syntax. The return value is an internal representation, which is typically an array structure containing values and expressions. Each part of the query has a different structure.
The single argument to the getPart() method is a string
that identifies which part of the Select query to return. For example, the string
'from' identifies the part of the Select object that stores
information about the tables in the FROM clause, including
joined tables.
The Zend_Db_Select class defines constants you can use for
parts of the SQL query. You can use these constant definitions,
or you can the literal strings.
Table 65. Constants used by getPart() and reset()
| Constant | String value |
|---|---|
Zend_Db_Select::DISTINCT |
'distinct' |
Zend_Db_Select::FOR_UPDATE |
'forupdate' |
Zend_Db_Select::COLUMNS |
'columns' |
Zend_Db_Select::FROM |
'from' |
Zend_Db_Select::WHERE |
'where' |
Zend_Db_Select::GROUP |
'group' |
Zend_Db_Select::HAVING |
'having' |
Zend_Db_Select::ORDER |
'order' |
Zend_Db_Select::LIMIT_COUNT |
'limitcount' |
Zend_Db_Select::LIMIT_OFFSET |
'limitoffset' |
Example 257. Example of the getPart() method
<?php
$select = $db->select()
->from('products')
->order('product_id');
// You can use a string literal to specify the part
$orderData = $select->getPart( 'order' );
// You can use a constant to specify the same part
$orderData = $select->getPart( Zend_Db_Select::ORDER );
// The return value may be an array structure, not a string.
// Each part has a different structure.
print_r( $orderData );
The reset() method enables you to clear one specified part
of the SQL query, or else clear all parts of the
SQL query if you omit the argument.
The single argument is optional. You can specify the part of the query to clear,
using the same strings you used in the argument to the
getPart() method. The part of the query you specify is
reset to a default state.
If you omit the parameter, reset() changes all parts of the
query to their default state. This makes the Zend_Db_Select
object equivalent to a new object, as though you had just instantiated it.
Example 258. Example of the reset() method
<?php
// Build this query:
// SELECT p.*
// FROM "products" AS p
// ORDER BY "product_name"
$select = $db->select()
->from(array('p' => 'products')
->order('product_name');
// Changed requirement, instead order by a different columns:
// SELECT p.*
// FROM "products" AS p
// ORDER BY "product_id"
// Clear one part so we can redefine it
$select->reset( Zend_Db_Select::ORDER );
// And specify a different column
$select->order('product_id');
// Clear all parts of the query
$select->reset();