Index: t3lib/class.t3lib_db.php
===================================================================
--- t3lib/class.t3lib_db.php	(revision 6571)
+++ t3lib/class.t3lib_db.php	(working copy)
@@ -514,6 +514,29 @@
 	}
 
 	/**
+	 * Creates a SELECT SQL-statement to be used as subquery within another query.
+	 * BEWARE: This method should not be overriden within DBAL to prevent quoting from happening.
+	 * 
+	 * @param	string		$select_fields
+	 * @param	string		$from_table
+	 * @param	string		$where_clause
+	 * @return	string		Full SQL query for SELECT
+	 */
+	public function SELECTsubquery($select_fields, $from_table, $where_clause) {
+
+			// Table and fieldnames should be "SQL-injection-safe" when supplied to this function
+			// Build basic query:
+		$query = 'SELECT ' . $select_fields . ' FROM ' . $from_table .
+			(strlen($where_clause) > 0 ? ' WHERE ' . $where_clause : '');
+
+			// Return query:
+		if ($this->debugOutput || $this->store_lastBuiltQuery) {
+			$this->debug_lastBuiltQuery = $query;
+		}
+		return $query;
+	}
+
+	/**
 	 * Returns a WHERE clause that can find a value ($value) in a list field ($field)
 	 * For instance a record in the database might contain a list of numbers,
 	 * "34,234,5" (with no spaces between). This query would be able to select that
Index: t3lib/cache/backend/class.t3lib_cache_backend_dbbackend.php
===================================================================
--- t3lib/cache/backend/class.t3lib_cache_backend_dbbackend.php	(revision 6571)
+++ t3lib/cache/backend/class.t3lib_cache_backend_dbbackend.php	(working copy)
@@ -292,7 +292,7 @@
 		$GLOBALS['TYPO3_DB']->exec_DELETEquery(
 			$this->cacheTable,
 			'identifier IN (' .
-				$GLOBALS['TYPO3_DB']->SELECTquery(
+				$GLOBALS['TYPO3_DB']->SELECTsubquery(
 					'identifier',
 					$this->tagsTable,
 					$this->getQueryForTag($tag)
@@ -322,7 +322,7 @@
 			$GLOBALS['TYPO3_DB']->exec_DELETEquery(
 				$this->cacheTable,
 				'identifier IN (' .
-					$GLOBALS['TYPO3_DB']->SELECTquery(
+					$GLOBALS['TYPO3_DB']->SELECTsubquery(
 						'identifier',
 						$this->tagsTable,
 						implode(' OR ', $listQueryConditions)
@@ -347,7 +347,7 @@
 		$GLOBALS['TYPO3_DB']->exec_DELETEquery(
 			$this->tagsTable,
 			'identifier IN (' .
-				$GLOBALS['TYPO3_DB']->SELECTquery(
+				$GLOBALS['TYPO3_DB']->SELECTsubquery(
 					'identifier',
 					$this->cacheTable,
 					'crdate + lifetime < ' . $GLOBALS['EXEC_TIME'] . ' AND lifetime > 0'
Index: t3lib/class.t3lib_sqlparser.php
===================================================================
--- t3lib/class.t3lib_sqlparser.php	(revision 6574)
+++ t3lib/class.t3lib_sqlparser.php	(working copy)
@@ -247,6 +247,9 @@
 			}
 		} else return $this->parseError('No table to select from!',$parseString);
 
+			// Store current parseString in the result array for possible further processing (e.g., subquery support by DBAL)
+		$result['parseString'] = $parseString;
+
 			// Return result:
 		return $result;
 	}