diff --git a/mysql-test/r/select.result b/mysql-test/r/select.result
index ff59eadab0c..1b2533eec89 100644
--- a/mysql-test/r/select.result
+++ b/mysql-test/r/select.result
@@ -4456,4 +4456,88 @@ SELECT 1 FROM t2 JOIN t1 ON 1=1
 WHERE a != '1' AND NOT a >= b OR NOT ROW(b,a )<> ROW(a,a);
 1
 DROP TABLE t1,t2;
+#
+# Bug #49199: Optimizer handles incorrectly: 
+# field='const1' AND field='const2' in some cases
+
+CREATE TABLE t1(a DATETIME NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01');
+SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+a
+2001-01-01 00:00:00
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+Warnings:
+Note	1003	select '2001-01-01 00:00:00' AS `a` from `test`.`t1` where 1
+DROP TABLE t1;
+CREATE TABLE t1(a DATE NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01');
+SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+a
+2001-01-01
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+Warnings:
+Note	1003	select '2001-01-01' AS `a` from `test`.`t1` where 1
+DROP TABLE t1;
+CREATE TABLE t1(a TIMESTAMP NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01');
+SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+a
+2001-01-01 00:00:00
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+Warnings:
+Note	1003	select '2001-01-01 00:00:00' AS `a` from `test`.`t1` where 1
+DROP TABLE t1;
+CREATE TABLE t1(a DATETIME NOT NULL, b DATE NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01', '2001-01-01');
+SELECT * FROM t1 WHERE a='2001-01-01' AND a=b AND b='2001-01-01 00:00:00';
+a	b
+2001-01-01 00:00:00	2001-01-01
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01' AND a=b AND b='2001-01-01 00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+Warnings:
+Note	1003	select '2001-01-01 00:00:00' AS `a`,'2001-01-01' AS `b` from `test`.`t1` where 1
+DROP TABLE t1;
+CREATE TABLE t1(a DATETIME NOT NULL, b VARCHAR(20) NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01', '2001-01-01');
+SELECT * FROM t1 WHERE a='2001-01-01' AND a=b AND b='2001-01-01 00:00:00';
+a	b
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01' AND a=b AND b='2001-01-01 00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+Warnings:
+Note	1003	select '2001-01-01 00:00:00' AS `a`,'2001-01-01' AS `b` from `test`.`t1` where 0
+SELECT * FROM t1 WHERE a='2001-01-01 00:00:00' AND a=b AND b='2001-01-01';
+a	b
+2001-01-01 00:00:00	2001-01-01
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01 00:00:00' AND a=b AND b='2001-01-01';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+Warnings:
+Note	1003	select '2001-01-01 00:00:00' AS `a`,'2001-01-01' AS `b` from `test`.`t1` where 1
+DROP TABLE t1;
+CREATE TABLE t1(a DATETIME NOT NULL, b DATE NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01', '2001-01-01');
+SELECT x.a, y.a, z.a FROM t1 x 
+JOIN t1 y ON x.a=y.a 
+JOIN t1 z ON y.a=z.a 
+WHERE x.a='2001-01-01' AND z.a='2001-01-01 00:00:00';
+a	a	a
+2001-01-01 00:00:00	2001-01-01 00:00:00	2001-01-01 00:00:00
+EXPLAIN EXTENDED SELECT x.a, y.a, z.a FROM t1 x 
+JOIN t1 y ON x.a=y.a 
+JOIN t1 z ON y.a=z.a 
+WHERE x.a='2001-01-01' AND z.a='2001-01-01 00:00:00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	x	system	NULL	NULL	NULL	NULL	1	
+1	SIMPLE	y	system	NULL	NULL	NULL	NULL	1	
+1	SIMPLE	z	system	NULL	NULL	NULL	NULL	1	
+Warnings:
+Note	1003	select '2001-01-01 00:00:00' AS `a`,'2001-01-01 00:00:00' AS `a`,'2001-01-01 00:00:00' AS `a` from `test`.`t1` `x` join `test`.`t1` `y` join `test`.`t1` `z` where 1
 End of 5.0 tests
diff --git a/mysql-test/t/select.test b/mysql-test/t/select.test
index a4d3056b66e..eeabd2641d8 100644
--- a/mysql-test/t/select.test
+++ b/mysql-test/t/select.test
@@ -3797,4 +3797,53 @@ SELECT 1 FROM t2 JOIN t1 ON 1=1
 DROP TABLE t1,t2;
 
 
+--echo #
+--echo # Bug #49199: Optimizer handles incorrectly: 
+--echo # field='const1' AND field='const2' in some cases
+--echo
+CREATE TABLE t1(a DATETIME NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01');
+SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+DROP TABLE t1;
+
+CREATE TABLE t1(a DATE NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01');
+SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+DROP TABLE t1;
+
+CREATE TABLE t1(a TIMESTAMP NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01');
+SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01' AND a='2001-01-01 00:00:00';
+DROP TABLE t1;
+
+CREATE TABLE t1(a DATETIME NOT NULL, b DATE NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01', '2001-01-01');
+SELECT * FROM t1 WHERE a='2001-01-01' AND a=b AND b='2001-01-01 00:00:00';
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01' AND a=b AND b='2001-01-01 00:00:00';
+DROP TABLE t1;
+
+CREATE TABLE t1(a DATETIME NOT NULL, b VARCHAR(20) NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01', '2001-01-01');
+SELECT * FROM t1 WHERE a='2001-01-01' AND a=b AND b='2001-01-01 00:00:00';
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01' AND a=b AND b='2001-01-01 00:00:00';
+
+SELECT * FROM t1 WHERE a='2001-01-01 00:00:00' AND a=b AND b='2001-01-01';
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='2001-01-01 00:00:00' AND a=b AND b='2001-01-01';
+DROP TABLE t1;
+
+CREATE TABLE t1(a DATETIME NOT NULL, b DATE NOT NULL);
+INSERT INTO t1 VALUES('2001-01-01', '2001-01-01');
+SELECT x.a, y.a, z.a FROM t1 x 
+  JOIN t1 y ON x.a=y.a 
+  JOIN t1 z ON y.a=z.a 
+  WHERE x.a='2001-01-01' AND z.a='2001-01-01 00:00:00';
+EXPLAIN EXTENDED SELECT x.a, y.a, z.a FROM t1 x 
+  JOIN t1 y ON x.a=y.a 
+  JOIN t1 z ON y.a=z.a 
+  WHERE x.a='2001-01-01' AND z.a='2001-01-01 00:00:00';
+
+
 --echo End of 5.0 tests
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index d03c68b3560..5c2fb9857d5 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -4903,7 +4903,8 @@ Item *Item_bool_rowready_func2::negated_item()
 }
 
 Item_equal::Item_equal(Item_field *f1, Item_field *f2)
-  : Item_bool_func(), const_item(0), eval_item(0), cond_false(0)
+  : Item_bool_func(), const_item(0), eval_item(0), cond_false(0),
+    compare_as_dates(FALSE)
 {
   const_item_cache= 0;
   fields.push_back(f1);
@@ -4916,6 +4917,7 @@ Item_equal::Item_equal(Item *c, Item_field *f)
   const_item_cache= 0;
   fields.push_back(f);
   const_item= c;
+  compare_as_dates= f->is_datetime();
 }
 
 
@@ -4930,9 +4932,45 @@ Item_equal::Item_equal(Item_equal *item_equal)
     fields.push_back(item);
   }
   const_item= item_equal->const_item;
+  compare_as_dates= item_equal->compare_as_dates;
   cond_false= item_equal->cond_false;
 }
 
+
+void Item_equal::compare_const(Item *c)
+{
+  if (compare_as_dates)
+  {
+    cmp.set_datetime_cmp_func(&c, &const_item);
+    cond_false= cmp.compare();
+  }
+  else
+  {
+    Item_func_eq *func= new Item_func_eq(c, const_item);
+    func->set_cmp_func();
+    func->quick_fix_field();
+    cond_false= !func->val_int();
+  }
+  if (cond_false)
+    const_item_cache= 1;
+}
+
+
+void Item_equal::add(Item *c, Item_field *f)
+{
+  if (cond_false)
+    return;
+  if (!const_item)
+  {
+    DBUG_ASSERT(f);
+    const_item= c;
+    compare_as_dates= f->is_datetime();
+    return;
+  }
+  compare_const(c);
+}
+
+
 void Item_equal::add(Item *c)
 {
   if (cond_false)
@@ -4942,11 +4980,7 @@ void Item_equal::add(Item *c)
     const_item= c;
     return;
   }
-  Item_func_eq *func= new Item_func_eq(c, const_item);
-  func->set_cmp_func();
-  func->quick_fix_field();
-  if ((cond_false= !func->val_int()))
-    const_item_cache= 1;
+  compare_const(c);
 }
 
 void Item_equal::add(Item_field *f)
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index db831c7030c..89bc6f9570b 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -1477,7 +1477,9 @@ class Item_equal: public Item_bool_func
   List<Item_field> fields; /* list of equal field items                    */
   Item *const_item;        /* optional constant item equal to fields items */
   cmp_item *eval_item;
+  Arg_comparator cmp;
   bool cond_false;
+  bool compare_as_dates;
 public:
   inline Item_equal()
     : Item_bool_func(), const_item(0), eval_item(0), cond_false(0)
@@ -1486,6 +1488,8 @@ public:
   Item_equal(Item *c, Item_field *f);
   Item_equal(Item_equal *item_equal);
   inline Item* get_const() { return const_item; }
+  void compare_const(Item *c);
+  void add(Item *c, Item_field *f);
   void add(Item *c);
   void add(Item_field *f);
   uint members();
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index df7c5af3ebc..9f0843fe0db 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -7237,7 +7237,7 @@ static bool check_simple_equality(Item *left_item, Item *right_item,
           already contains a constant and its value is  not equal to
           the value of const_item.
         */
-        item_equal->add(const_item);
+        item_equal->add(const_item, field_item);
       }
       else
       {