pager_query

• Drupal 4.6
• Drupal 4.7
• Drupal 5
• Drupal 6

Versions

4.6 – 6

pager_query($query, $limit = 10, $element = 0, $count_query = NULL)

Perform a paged database query.

Use this function when doing select queries you wish to be able to page. The pager uses LIMIT-based queries to fetch only the records required to render a certain page. However, it has to learn the total number of records returned by the query to compute the number of pages (the number of records / records per page). This is done by inserting "COUNT(*)" in the original query. For example, the query "SELECT nid, type FROM node WHERE status = '1' ORDER BY sticky DESC, created DESC" would be rewritten to read "SELECT COUNT(*) FROM node WHERE status = '1' ORDER BY sticky DESC, created DESC". Rewriting the query is accomplished using a regular expression.

Unfortunately, the rewrite rule does not always work as intended for queries that already have a "COUNT(*)" or a "GROUP BY" clause, and possibly for other complex queries. In those cases, you can optionally pass a query that will be used to count the records.

For example, if you want to page the query "SELECT COUNT(*), TYPE FROM node GROUP BY TYPE", pager_query() would invoke the incorrect query "SELECT COUNT(*) FROM node GROUP BY TYPE". So instead, you should pass "SELECT COUNT(DISTINCT(TYPE)) FROM node" as the optional $count_query parameter.

Parameters

$query The SQL query that needs paging.

$limit The number of query results to display per page.

$element An optional integer to distinguish between multiple pagers on one page.

$count_query An SQL query used to count matching records.

... A variable number of arguments which are substituted into the query (and the count query) using printf() syntax. Instead of a variable number of query arguments, you may also pass a single array containing the query arguments.

Return value

A database query result resource, or FALSE if the query was not executed correctly.

Related topics

Database abstraction layer

Allow the use of different database servers using the same code base.

Code

includes/pager.inc, line 50

<?php
function pager_query($query, $limit = 10, $element = 0, $count_query = NULL) {
  global $pager_page_array, $pager_total, $pager_total_items;
  $page = isset($_GET['page']) ? $_GET['page'] : '';

  // Substitute in query arguments.
  $args = func_get_args();
  $args = array_slice($args, 4);
  // Alternative syntax for '...'
  if (isset($args[0]) && is_array($args[0])) {
    $args = $args[0];
  }

  // Construct a count query if none was given.
  if (!isset($count_query)) {
    $count_query = preg_replace(array('/SELECT.*?FROM /As', '/ORDER BY .*/'), array('SELECT COUNT(*) FROM ', ''), $query);
  }

  // Convert comma-separated $page to an array, used by other functions.
  $pager_page_array = explode(',', $page);

  // We calculate the total of pages as ceil(items / limit).
  $pager_total_items[$element] = db_result(db_query($count_query, $args));
  $pager_total[$element] = ceil($pager_total_items[$element] / $limit);
  $pager_page_array[$element] = max(0, min((int)$pager_page_array[$element], ((int)$pager_total[$element]) - 1));
  return db_query_range($query, $args, $pager_page_array[$element] * $limit, $limit);
}
?>

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