select.result, select.test:

  Added test cases for bug #6474.
sql_select.cc:
  Fixed bug #6474. A wrong result was returned when a query
  contained the same equality of the form field=const on
  different AND levels.

mysql-test/r/select.result

@@ -2333,3 +2333,36 @@ EXPLAIN SELECT i FROM t1 WHERE i=1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	const	PRIMARY	PRIMARY	4	const	1	Using index
 DROP TABLE t1;
+CREATE TABLE t1 ( 
+K2C4 varchar(4) character set latin1 collate latin1_bin NOT NULL default '', 
+K4N4 varchar(4) character set latin1 collate latin1_bin NOT NULL default '0000', 
+F2I4 int(11) NOT NULL default '0' 
+) ENGINE=MyISAM DEFAULT CHARSET=latin1;
+INSERT INTO t1 VALUES 
+('W%RT', '0100',  1), 
+('W-RT', '0100', 1), 
+('WART', '0100', 1), 
+('WART', '0200', 1), 
+('WERT', '0100', 2), 
+('WORT','0200', 2), 
+('WT', '0100', 2), 
+('W_RT', '0100', 2), 
+('WaRT', '0100', 3), 
+('WART', '0300', 3), 
+('WRT' , '0400', 3), 
+('WURM', '0500', 3), 
+('W%T', '0600', 4), 
+('WA%T', '0700', 4), 
+('WA_T', '0800', 4);
+SELECT K2C4, K4N4, F2I4 FROM t1
+WHERE  K2C4 = 'WART' AND 
+(F2I4 = 2 AND K2C4 = 'WART' OR (F2I4 = 2 OR K4N4 = '0200'));
+K2C4	K4N4	F2I4
+WART	0200	1
+SELECT K2C4, K4N4, F2I4 FROM t1
+WHERE  K2C4 = 'WART' AND (K2C4 = 'WART' OR K4N4 = '0200');
+K2C4	K4N4	F2I4
+WART	0100	1
+WART	0200	1
+WART	0300	3
+DROP TABLE t1;

mysql-test/t/select.test

@@ -1910,3 +1910,39 @@ EXPLAIN SELECT i FROM t1 WHERE i=1;
 EXPLAIN SELECT i FROM t1 WHERE i=1;
 
 DROP TABLE t1;
+
+#
+# Test for bug #6474
+#
+
+CREATE TABLE t1 ( 
+K2C4 varchar(4) character set latin1 collate latin1_bin NOT NULL default '', 
+K4N4 varchar(4) character set latin1 collate latin1_bin NOT NULL default '0000', 
+F2I4 int(11) NOT NULL default '0' 
+) ENGINE=MyISAM DEFAULT CHARSET=latin1;
+
+INSERT INTO t1 VALUES 
+('W%RT', '0100',  1), 
+('W-RT', '0100', 1), 
+('WART', '0100', 1), 
+('WART', '0200', 1), 
+('WERT', '0100', 2), 
+('WORT','0200', 2), 
+('WT', '0100', 2), 
+('W_RT', '0100', 2), 
+('WaRT', '0100', 3), 
+('WART', '0300', 3), 
+('WRT' , '0400', 3), 
+('WURM', '0500', 3), 
+('W%T', '0600', 4), 
+('WA%T', '0700', 4), 
+('WA_T', '0800', 4);
+
+SELECT K2C4, K4N4, F2I4 FROM t1
+  WHERE  K2C4 = 'WART' AND 
+        (F2I4 = 2 AND K2C4 = 'WART' OR (F2I4 = 2 OR K4N4 = '0200'));
+
+SELECT K2C4, K4N4, F2I4 FROM t1
+  WHERE  K2C4 = 'WART' AND (K2C4 = 'WART' OR K4N4 = '0200');
+
+DROP TABLE t1;

sql/sql_select.cc

@@ -6639,10 +6639,7 @@ static Item *eliminate_item_equal(COND *cond, COND_EQUAL *upper_levels,
   List<Item> eq_list;
   Item_func_eq *eq_item= 0;
   if (((Item *) item_equal)->const_item() && !item_equal->val_int())
-  {
-    cond= new Item_int((char*) "FALSE",0,1);
-    return cond;
-  } 
+    return new Item_int((longlong) 0,1); 
   Item *item_const= item_equal->get_const();
   Item_equal_iterator it(*item_equal);
   Item *head;
@@ -6685,9 +6682,14 @@ static Item *eliminate_item_equal(COND *cond, COND_EQUAL *upper_levels,
   }
 
   if (!cond && !eq_list.head())
+  {
+    if (!eq_item)
+      return new Item_int((longlong) 1,1);
     return eq_item;
+  }
 
-  eq_list.push_back(eq_item);
+  if (eq_item)
+    eq_list.push_back(eq_item);
   if (!cond)
     cond= new Item_cond_and(eq_list);
   else