Fixed bug #18618.

If the second or the third argument of a BETWEEN predicate was
a constant expression, like '2005.09.01' - INTERVAL 6 MONTH,
while the other two arguments were fields then the predicate 
was evaluated incorrectly and the query returned a wrong
result set.
The bug was introduced in 5.0.17 when in the fix for 12612.

mysql-test/r/func_time.result

@@ -847,3 +847,28 @@ timestampdiff(year,'2004-02-28','2005-02-28')
 select timestampdiff(year,'2004-02-29','2005-02-28');
 timestampdiff(year,'2004-02-29','2005-02-28')
 0
+CREATE TABLE t1 (id int NOT NULL PRIMARY KEY, day date);
+CREATE TABLE t2 (id int NOT NULL PRIMARY KEY, day date);
+INSERT INTO t1 VALUES
+(1, '2005-06-01'), (2, '2005-02-01'), (3, '2005-07-01');
+INSERT INTO t2 VALUES
+(1, '2005-08-01'), (2, '2005-06-15'), (3, '2005-07-15');
+SELECT * FROM t1, t2 
+WHERE t1.day BETWEEN 
+'2005.09.01' - INTERVAL 6 MONTH AND t2.day;
+id	day	id	day
+1	2005-06-01	1	2005-08-01
+3	2005-07-01	1	2005-08-01
+1	2005-06-01	2	2005-06-15
+1	2005-06-01	3	2005-07-15
+3	2005-07-01	3	2005-07-15
+SELECT * FROM t1, t2 
+WHERE CAST(t1.day AS DATE) BETWEEN 
+'2005.09.01' - INTERVAL 6 MONTH AND t2.day;
+id	day	id	day
+1	2005-06-01	1	2005-08-01
+3	2005-07-01	1	2005-08-01
+1	2005-06-01	2	2005-06-15
+1	2005-06-01	3	2005-07-15
+3	2005-07-01	3	2005-07-15
+DROP TABLE t1,t2;

mysql-test/t/func_time.test

@@ -446,4 +446,26 @@ select timestampdiff(year,'1999-09-11','2001-9-11');
 select timestampdiff(year,'2004-02-28','2005-02-28');
 select timestampdiff(year,'2004-02-29','2005-02-28');
 
+#
+# Bug #18618: BETWEEN for dates with the second argument being a constant
+#             expression and the first and the third arguments being fields 
+#
+
+CREATE TABLE t1 (id int NOT NULL PRIMARY KEY, day date);
+CREATE TABLE t2 (id int NOT NULL PRIMARY KEY, day date);
+
+INSERT INTO t1 VALUES
+  (1, '2005-06-01'), (2, '2005-02-01'), (3, '2005-07-01');
+INSERT INTO t2 VALUES
+  (1, '2005-08-01'), (2, '2005-06-15'), (3, '2005-07-15');
+
+SELECT * FROM t1, t2 
+  WHERE t1.day BETWEEN 
+               '2005.09.01' - INTERVAL 6 MONTH AND t2.day;
+SELECT * FROM t1, t2 
+  WHERE CAST(t1.day AS DATE) BETWEEN 
+                             '2005.09.01' - INTERVAL 6 MONTH AND t2.day;
+ 
+DROP TABLE t1,t2;
+
 # End of 5.0 tests

sql/item_cmpfunc.cc

@@ -52,7 +52,6 @@ static void agg_cmp_type(THD *thd, Item_result *type, Item **items, uint nitems)
 {
   uint i;
   Field *field= NULL;
-  bool all_constant= TRUE;
 
   /* If the first argument is a FIELD_ITEM, pull out the field. */
   if (items[0]->real_item()->type() == Item::FIELD_ITEM)
@@ -65,16 +64,9 @@ static void agg_cmp_type(THD *thd, Item_result *type, Item **items, uint nitems)
   for (i= 1; i < nitems; i++)
   {
     type[0]= item_cmp_type(type[0], items[i]->result_type());
-    if (field && !convert_constant_item(thd, field, &items[i]))
-      all_constant= FALSE;
+    if (field && convert_constant_item(thd, field, &items[i]))
+      type[0]= INT_RESULT;
   }
-
-  /*
-    If we had a field that can be compared as a longlong, and all constant
-    items, then the aggregate result will be an INT_RESULT.
-  */
-  if (field && all_constant)
-    type[0]= INT_RESULT;
 }