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Definition

db_distinct_field($table, $field, $query)
drupal/includes/database.pgsql.inc, line 419

Description

Wraps the given table.field entry with a DISTINCT(). The wrapper is added to the SELECT list entry of the given query and the resulting query is returned. This function only applies the wrapper if a DISTINCT doesn't already exist in the query.

Parameters

$table Table containing the field to set as DISTINCT

$field Field to set as DISTINCT

$query Query to apply the wrapper to

Return value

SQL query with the DISTINCT wrapper surrounding the given table.field.

Related topics

Name	Description
Database abstraction layer	Allow the use of different database servers using the same code base.

Code

function db_distinct_field($table, $field, $query) {
  $field_to_select = 'DISTINCT ON ('. $table .'.'. $field .") $table.$field";
  // (?<!text) is a negative look-behind (no need to rewrite queries that already use DISTINCT).
  $query = preg_replace('/(SELECT.*)(?:'. $table .'\.|\s)(?<!DISTINCT\()(?<!DISTINCT\('. $table .'\.)'. $field .'(.*FROM )/AUsi', '\1 '. $field_to_select .'\2', $query);
  $query = preg_replace('/(ORDER BY )(?!'.$table.'\.'.$field.')/', '\1'."$table.$field, ", $query);
  return $query;
}