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db_distinct_field

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    6. 5 database.pgsql.inc
    7. 6 database.inc
Versions
4.7 – 6 db_distinct_field($table, $field, $query)

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

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

Code

includes/database.mysqli.inc, line 420

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