1 files changed, 21 insertions, 23 deletions
diff --git a/phpBB/includes/db/dbal.php b/phpBB/includes/db/dbal.php
index c4ae50dea0..b530a572da 100644
--- a/phpBB/includes/db/dbal.php
+++ b/phpBB/includes/db/dbal.php
@@ -502,10 +502,14 @@ class dbal
 
 				// Build table array. We also build an alias array for later checks.
 				$table_array = $aliases = array();
+				$used_multi_alias = false;
+
 				foreach ($array['FROM'] as $table_name => $alias)
 				{
 					if (is_array($alias))
 					{
+						$used_multi_alias = true;
+
 						foreach ($alias as $multi_alias)
 						{
 							$table_array[] = $table_name . ' ' . $multi_alias;
@@ -520,11 +524,9 @@ class dbal
 				}
 
 				// We run the following code to determine if we need to re-order the table array. ;)
-				// The reason for this is that for multiple tables in the FROM statement the last table need to match the first LEFT JOIN'ed table.
-				// DBMS who rely on this (at the moment i only spotted it on multi-aliases): Oracle, PostgreSQL and MSSQL
-				$first_join_match = false;
-
-				if (!empty($array['LEFT_JOIN']) && sizeof($array['FROM']) > 1)
+				// The reason for this is that for multi-aliased tables (two equal tables) in the FROM statement the last table need to match the first comparison.
+				// DBMS who rely on this: Oracle, PostgreSQL and MSSQL. For all other DBMS it makes absolutely no difference in which order the table is.
+				if (!empty($array['LEFT_JOIN']) && sizeof($array['FROM']) > 1 && $used_multi_alias !== false)
 				{
 					// Take first LEFT JOIN
 					$join = current($array['LEFT_JOIN']);
@@ -532,33 +534,29 @@ class dbal
 					// Determine the table used there (even if there are more than one used, we only want to have one
 					preg_match('/(' . implode('|', $aliases) . ')\.[^\s]+/U', str_replace(array('(', ')', 'AND', 'OR', ' '), '', $join['ON']), $matches);
 
+					// If there is a first join match, we need to make sure the table order is correct
 					if (!empty($matches[1]))
 					{
 						$first_join_match = trim($matches[1]);
-					}
-				}
-
-				// If there is a first join match, we need to make sure the table order is correct
-				if ($first_join_match !== false)
-				{
-					$table_array = $last = array();
+						$table_array = $last = array();
 
-					foreach ($array['FROM'] as $table_name => $alias)
-					{
-						if (is_array($alias))
+						foreach ($array['FROM'] as $table_name => $alias)
 						{
-							foreach ($alias as $multi_alias)
+							if (is_array($alias))
 							{
-								($multi_alias === $first_join_match) ? $last[] = $table_name . ' ' . $multi_alias : $table_array[] = $table_name . ' ' . $multi_alias;
+								foreach ($alias as $multi_alias)
+								{
+									($multi_alias === $first_join_match) ? $last[] = $table_name . ' ' . $multi_alias : $table_array[] = $table_name . ' ' . $multi_alias;
+								}
+							}
+							else
+							{
+								($alias === $first_join_match) ? $last[] = $table_name . ' ' . $alias : $table_array[] = $table_name . ' ' . $alias;
 							}
 						}
-						else
-						{
-							($alias === $first_join_match) ? $last[] = $table_name . ' ' . $alias : $table_array[] = $table_name . ' ' . $alias;
-						}
-					}
 
-					$table_array = array_merge($table_array, $last);
+						$table_array = array_merge($table_array, $last);
+					}
 				}
 
 				$sql .= $this->_sql_custom_build('FROM', implode(', ', $table_array));