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Difference between revisions of "Selecting data using JDatabase"

From Joomla! Documentation

(Updates)
(Start moving functions across to new syntax)
Line 29: Line 29:
  
 
This is often the result of a 'count' query to get a number of records:
 
This is often the result of a 'count' query to get a number of records:
<source lang='php'>
+
<source lang="php">
$db = JFactory::getDBO();
+
$db = JFactory::getDbo();
$query = "
+
$query = $db->getQuery(true);
  SELECT COUNT(*)
+
$query->select('COUNT(*)');
    FROM ".$db->nameQuote('#__my_table')."
+
$query->from('#__my_table');
    WHERE ".$db->nameQuote('name')." = ".$db->quote($value).";
+
$query->where($db->nameQuote('name')." = ".$db->quote($value));
  ";
+
 
 +
// Reset the query using our newly populated query object.
 
$db->setQuery($query);
 
$db->setQuery($query);
 
$count = $db->loadResult();
 
$count = $db->loadResult();
Line 41: Line 42:
 
or where you are just looking for a single field from a single row of the table (or possibly a single field from the first row returned).
 
or where you are just looking for a single field from a single row of the table (or possibly a single field from the first row returned).
 
<source lang='php'>
 
<source lang='php'>
$db = JFactory::getDBO();
+
$db = JFactory::getDbo();
$query = "
+
$query = $db->getQuery(true);
  SELECT ".$db->nameQuote('field_name')."
+
$query->select('field_name');
    FROM ".$db->nameQuote('#__my_table')."
+
$query->from('#__my_table');
    WHERE ".$db->nameQuote('some_name')." = ".$db->quote($some_value).";
+
$query->where($db->nameQuote('some_name')." = ".$db->quote($some_value));
  ";
+
 
 
$db->setQuery($query);
 
$db->setQuery($query);
 
$result = $db->loadResult();
 
$result = $db->loadResult();

Revision as of 21:19, 30 August 2013

There are two parts to JDatabase:

  1. Building a query - this allows you to be multi-database compatible.
  2. Retrieving the results of a query - allowing you to retrieve the contents of your database query in a number of ways.

This section of the documentation looks at retrieving that query from the database with JDatabase in a variety of formats.

Contents

Introduction

Joomla provides a sophisticated database abstraction layer to simplify the usage for third party developers. New versions of the Joomla Platform API provide additional functionality which extends the database layer further, and includes features such as connectors to a greater variety of database servers and the query chaining to improve readability of connection code and simplify SQL coding.

Joomla can use different kinds of SQL database systems and run in a variety of environments with different table-prefixes. In addition to these functions, the class automatically creates the database connection. Besides instantiating the object you need just two lines of code to get a result from the database in a variety of formats. Using the Joomla database layer ensures a maximum of compatibility and flexibility for your extension.

Query Results

The database class contains many methods for working with a query's result set.

Single Value Result

loadResult()

Use loadResult() when you expect just a single value back from your database query.

id name email username
1 John Smith johnsmith@domain.example johnsmith
2 Magda Hellman magda_h@domain.example magdah
3 Yvonne de Gaulle ydg@domain.example ydegaulle

This is often the result of a 'count' query to get a number of records:

$db = JFactory::getDbo();
$query = $db->getQuery(true);
$query->select('COUNT(*)');
$query->from('#__my_table');
$query->where($db->nameQuote('name')." = ".$db->quote($value));
 
// Reset the query using our newly populated query object.
$db->setQuery($query);
$count = $db->loadResult();

or where you are just looking for a single field from a single row of the table (or possibly a single field from the first row returned).

$db = JFactory::getDbo();
$query = $db->getQuery(true);
$query->select('field_name');
$query->from('#__my_table');
$query->where($db->nameQuote('some_name')." = ".$db->quote($some_value));
 
$db->setQuery($query);
$result = $db->loadResult();

Single Row Results

Each of these results functions will return a single record from the database even though there may be several records that meet the criteria that you have set. To get more records you need to call the function again.

id name email username
1 John Smith johnsmith@domain.example johnsmith
2 Magda Hellman magda_h@domain.example magdah
3 Yvonne de Gaulle ydg@domain.example ydegaulle

loadRow()

loadRow() returns an indexed array from a single record in the table:

. . .
$db->setQuery($query);
$row = $db->loadRow();
print_r($row);

will give:

Array ( [0] => 1 [1] => John Smith [2] => johnsmith@domain.example [3] => johnsmith ) 

You can access the individual values by using:

$row['index'] // e.g. $row['2']

Notes:

  1. The array indices are numeric starting from zero.
  2. Whilst you can repeat the call to get further rows, one of the functions that returns multiple rows might be more useful.

loadAssoc()

loadAssoc() returns an associated array from a single record in the table:

. . .
$db->setQuery($query);
$row = $db->loadAssoc();
print_r($row);

will give:

Array ( [id] => 1 [name] => John Smith [email] => johnsmith@domain.example [username] => johnsmith )

You can access the individual values by using:

$row['name'] // e.g. $row['name']

Notes:

  1. Whilst you can repeat the call to get further rows, one of the functions that returns multiple rows might be more useful.

loadObject()

loadObject returns a PHP object from a single record in the table:

. . .
$db->setQuery($query);
$result = $db->loadObject();
print_r($result);

will give:

stdClass Object ( [id] => 1 [name] => John Smith [email] => johnsmith@domain.example [username] => johnsmith )

You can access the individual values by using:

$result->index // e.g. $result->email

Notes:

  1. Whilst you can repeat the call to get further rows, one of the functions that returns multiple rows might be more useful.

Single Column Results

Each of these results functions will return a single column from the database.

id name email username
1 John Smith johnsmith@domain.example johnsmith
2 Magda Hellman magda_h@domain.example magdah
3 Yvonne de Gaulle ydg@domain.example ydegaulle

loadColumn()

loadColumn() returns an indexed array from a single column in the table:

$query = "
  SELECT name, email, username
    FROM . . . ";
. . .
$db->setQuery($query);
$column= $db->loadColumn();
print_r($column);

will give:

Array ( [0] => John Smith [1] => Magda Hellman [2] => Yvonne de Gaulle )

You can access the individual values by using:

$column['index'] // e.g. $column['2']

Notes:

  1. The array indices are numeric starting from zero.
  2. loadColumn() is equivalent to loadColumn(0).

loadColumn($index)

loadColumn($index) returns an indexed array from a single column in the table:

$query = "
  SELECT name, email, username
    FROM . . . ";
. . .
$db->setQuery($query);
$column= $db->loadColumn(1);
print_r($column);

will give:

Array ( [0] => johnsmith@domain.example [1] => magda_h@domain.example [2] => ydg@domain.example )

You can access the individual values by using:

$column['index'] // e.g. $column['2']

loadColumn($index) allows you to iterate through a series of columns in the results

. . .
$db->setQuery($query);
for ( $i = 0; $i <= 2; $i++ ) {
  $column= $db->loadColumn($i);
  print_r($column);
}

will give:

Array ( [0] => John Smith [1] => Magda Hellman [2] => Yvonne de Gaulle )
Array ( [0] => johnsmith@domain.example [1] => magda_h@domain.example [2] => ydg@domain.example )
Array ( [0] => johnsmith [1] => magdah [2] => ydegaulle )

Notes:

  1. The array indices are numeric starting from zero.

Multi-Row Results

Each of these results functions will return multiple records from the database.

id name email username
1 John Smith johnsmith@domain.example johnsmith
2 Magda Hellman magda_h@domain.example magdah
3 Yvonne de Gaulle ydg@domain.example ydegaulle

loadRowList()

loadRowList() returns an indexed array of indexed arrays from the table records returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadRowList();
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[0] => Array ( [0] => 1 [1] => John Smith [2] => johnsmith@domain.example [3] => johnsmith ) 
[1] => Array ( [0] => 2 [1] => Magda Hellman [2] => magda_h@domain.example [3] => magdah ) 
[2] => Array ( [0] => 3 [1] => Yvonne de Gaulle [2] => ydg@domain.example [3] => ydegaulle ) 
)

You can access the individual rows by using:

$row['index'] // e.g. $row['2']

and you can access the individual values by using:

$row['index']['index'] // e.g. $row['2']['3']

Notes:

  1. The array indices are numeric starting from zero.

loadAssocList()

loadAssocList() returns an indexed array of associated arrays from the table records returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadAssocList();
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[0] => Array ( [id] => 1 [name] => John Smith [email] => johnsmith@domain.example [username] => johnsmith ) 
[1] => Array ( [id] => 2 [name] => Magda Hellman [email] => magda_h@domain.example [username] => magdah ) 
[2] => Array ( [id] => 3 [name] => Yvonne de Gaulle [email] => ydg@domain.example [username] => ydegaulle ) 
) 

You can access the individual rows by using:

$row['index'] // e.g. $row['2']

and you can access the individual values by using:

$row['index']['column_name'] // e.g. $row['2']['email']

loadAssocList($key)

loadAssocList('key') returns an associated array - indexed on 'key' - of associated arrays from the table records returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadAssocList('username');
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[johnsmith] => Array ( [id] => 1 [name] => John Smith [email] => johnsmith@domain.example [username] => johnsmith ) 
[magdah] => Array ( [id] => 2 [name] => Magda Hellman [email] => magda_h@domain.example [username] => magdah ) 
[ydegaulle] => Array ( [id] => 3 [name] => Yvonne de Gaulle [email] => ydg@domain.example [username] => ydegaulle ) 
)

You can access the individual rows by using:

$row['key_value'] // e.g. $row['johnsmith']

and you can access the individual values by using:

$row['key_value']['column_name'] // e.g. $row['johnsmith']['email']

Note: Key must be a valid column name from the table; it does not have to be an Index or a Primary Key. But if it does not have a unique value you may not be able to retrieve results reliably.

loadObjectList()

loadObjectList() returns an indexed array of PHP objects from the table records returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadObjectList();
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[0] => stdClass Object ( [id] => 1 [name] => John Smith 
    [email] => johnsmith@domain.example [username] => johnsmith ) 
[1] => stdClass Object ( [id] => 2 [name] => Magda Hellman 
    [email] => magda_h@domain.example [username] => magdah ) 
[2] => stdClass Object ( [id] => 3 [name] => Yvonne de Gaulle 
    [email] => ydg@domain.example [username] => ydegaulle ) 
)

You can access the individual rows by using:

$row['index'] // e.g. $row['2']

and you can access the individual values by using:

$row['index']->name // e.g. $row['2']->email

loadObjectList('key')

loadObjectList($key) returns an associated array - indexed on 'key' - of objects from the table records returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadObjectList('username');
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[johnsmith] => stdClass Object ( [id] => 1 [name] => John Smith 
    [email] => johnsmith@domain.example [username] => johnsmith ) 
[magdah] => stdClass Object ( [id] => 2 [name] => Magda Hellman 
    [email] => magda_h@domain.example [username] => magdah ) 
[ydegaulle] => stdClass Object ( [id] => 3 [name] => Yvonne de Gaulle 
    [email] => ydg@domain.example [username] => ydegaulle ) 
)

You can access the individual rows by using:

$row['key_value'] // e.g. $row['johnsmith']

and you can access the individual values by using:

$row['key_value']->column_name // e.g. $row['johnsmith']->email

Note: Key must be a valid column name from the table; it does not have to be an Index or a Primary Key. But if it does not have a unique value you may not be able to retrieve results reliably.

Miscellaneous Result Set Methods

getNumRows()

getNumRows() will return the number of result rows found by the last query and waiting to be read. To get a result from getNumRows() you have to run it after the query and before you have retrieved any results.

. . .
$db->setQuery($query);
$db->query();
$num_rows = $db->getNumRows();
print_r($num_rows);
$result = $db->loadRowList();

will return

3

Note: if you run getNumRows() after loadRowList() - or any other retrieval method - you may get a PHP Warning:

Warning: mysql_num_rows(): 80 is not a valid MySQL result resource 
in D:\xampp\htdocs\joomla1.5a\libraries\joomla\database\database\mysql.php on line 344