diff --git a/mysql-test/r/join.result b/mysql-test/r/join.result
index 9f87ea082db..7524de2368f 100644
--- a/mysql-test/r/join.result
+++ b/mysql-test/r/join.result
@@ -1184,4 +1184,75 @@ NULL
 NULL
 1
 DROP TABLE t1, t2, mm1;
+#
+# Bug #55568: user variable assignments crash server when used within
+#             query
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (0), (1);
+SELECT MULTIPOINT(
+1,
+(
+SELECT MULTIPOINT(
+MULTIPOINT(
+1,
+(SELECT COUNT(*) FROM (SELECT 1 FROM t1 GROUP BY a,a) d)
+)
+) FROM t1
+)
+) != COUNT(*) q FROM t1 GROUP BY a;
+q
+NULL
+NULL
+SELECT MULTIPOINT(
+1,
+(
+SELECT MULTIPOINT(
+MULTIPOINT(
+1,
+(SELECT COUNT(*) FROM (SELECT 1 FROM t1 GROUP BY a,a) d)
+)
+) FROM t1
+)
+) != COUNT(*) q FROM t1 GROUP BY a;
+q
+NULL
+NULL
+DROP TABLE t1;
+#
+# Bug #54468: crash after item's print() function when ordering/grouping 
+#             by subquery
+#
+CREATE TABLE t1(a INT, b INT);
+INSERT INTO t1 VALUES (), ();
+SELECT 1 FROM t1
+GROUP BY
+GREATEST(t1.a,
+(SELECT 1 FROM
+(SELECT t1.b FROM t1,t1 t2
+ORDER BY t1.a, t1.a LIMIT 1) AS d)
+);
+1
+1
+DROP TABLE t1;
+#
+# Bug #53544: Server hangs during JOIN query in stored procedure called
+#             twice in a row
+#
+CREATE TABLE t1(c INT);
+INSERT INTO t1 VALUES (1), (2);
+PREPARE stmt FROM "SELECT t2.c AS f1 FROM t1 LEFT JOIN
+                                        t1 t2 ON t1.c=t2.c RIGHT JOIN
+                                        t1 t3 ON t1.c=t3.c 
+                   GROUP BY f1;";
+EXECUTE stmt;
+f1
+1
+2
+EXECUTE stmt;
+f1
+1
+2
+DEALLOCATE PREPARE stmt;
+DROP TABLE t1;
 End of 5.1 tests
diff --git a/mysql-test/t/join.test b/mysql-test/t/join.test
index 43b373c9703..73a1ae5eb82 100644
--- a/mysql-test/t/join.test
+++ b/mysql-test/t/join.test
@@ -851,4 +851,70 @@ ENGINE=MERGE  UNION=(t1,t2);
 SELECT t1.a FROM mm1,t1;
 DROP TABLE t1, t2, mm1;
 
+--echo #
+--echo # Bug #55568: user variable assignments crash server when used within
+--echo #             query
+--echo #
+
+CREATE TABLE t1 (a INT);
+
+INSERT INTO t1 VALUES (0), (1);
+
+let $i=2;
+while ($i)
+{
+  SELECT MULTIPOINT(
+    1,
+    (
+      SELECT MULTIPOINT(
+        MULTIPOINT(
+          1,
+          (SELECT COUNT(*) FROM (SELECT 1 FROM t1 GROUP BY a,a) d)
+        )
+      ) FROM t1
+    )
+  ) != COUNT(*) q FROM t1 GROUP BY a;
+  dec $i;
+}
+
+DROP TABLE t1;
+
+--echo #
+--echo # Bug #54468: crash after item's print() function when ordering/grouping 
+--echo #             by subquery
+--echo #
+
+CREATE TABLE t1(a INT, b INT);
+INSERT INTO t1 VALUES (), ();
+
+SELECT 1 FROM t1
+GROUP BY
+GREATEST(t1.a,
+         (SELECT 1 FROM
+          (SELECT t1.b FROM t1,t1 t2
+           ORDER BY t1.a, t1.a LIMIT 1) AS d)
+        );
+
+DROP TABLE t1;
+
+--echo #
+--echo # Bug #53544: Server hangs during JOIN query in stored procedure called
+--echo #             twice in a row
+--echo #
+
+CREATE TABLE t1(c INT);
+
+INSERT INTO t1 VALUES (1), (2);
+
+PREPARE stmt FROM "SELECT t2.c AS f1 FROM t1 LEFT JOIN
+                                        t1 t2 ON t1.c=t2.c RIGHT JOIN
+                                        t1 t3 ON t1.c=t3.c 
+                   GROUP BY f1;";
+
+EXECUTE stmt;
+EXECUTE stmt;
+
+DEALLOCATE PREPARE stmt;
+DROP TABLE t1;
+
 --echo End of 5.1 tests
diff --git a/sql/field.cc b/sql/field.cc
index 3c93ffadac5..c9b5f980ae5 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -1564,7 +1564,7 @@ void Field::make_field(Send_field *field)
   }
   else
     field->org_table_name= field->db_name= "";
-  if (orig_table)
+  if (orig_table && orig_table->alias)
   {
     field->table_name= orig_table->alias;
     field->org_col_name= field_name;
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 2dabeeaa22e..77c9d564ec7 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -2402,13 +2402,8 @@ JOIN::destroy()
 
   cleanup(1);
  /* Cleanup items referencing temporary table columns */
-  if (!tmp_all_fields3.is_empty())
-  {
-    List_iterator_fast<Item> it(tmp_all_fields3);
-    Item *item;
-    while ((item= it++))
-      item->cleanup();
-  }
+  cleanup_item_list(tmp_all_fields1);
+  cleanup_item_list(tmp_all_fields3);
   if (exec_tmp_table1)
     free_tmp_table(thd, exec_tmp_table1);
   if (exec_tmp_table2)
@@ -2419,6 +2414,19 @@ JOIN::destroy()
   DBUG_RETURN(error);
 }
 
+
+void JOIN::cleanup_item_list(List<Item> &items) const
+{
+  if (!items.is_empty())
+  {
+    List_iterator_fast<Item> it(items);
+    Item *item;
+    while ((item= it++))
+      item->cleanup();
+  }
+}
+
+
 /**
   An entry point to single-unit select (a select without UNION).
 
@@ -9008,10 +9016,10 @@ simplify_joins(JOIN *join, List<TABLE_LIST> *join_list, COND *conds, bool top)
     
   /* Flatten nested joins that can be flattened. */
   TABLE_LIST *right_neighbor= NULL;
-  bool fix_name_res= FALSE;
   li.rewind();
   while ((table= li++))
   {
+    bool fix_name_res= FALSE;
     nested_join= table->nested_join;
     if (nested_join && !table->on_expr)
     {
diff --git a/sql/sql_select.h b/sql/sql_select.h
index 77fff4ee24c..93885e23f76 100644
--- a/sql/sql_select.h
+++ b/sql/sql_select.h
@@ -583,6 +583,7 @@ private:
   */
   bool implicit_grouping; 
   bool make_simple_join(JOIN *join, TABLE *tmp_table);
+  void cleanup_item_list(List<Item> &items) const;
 };