Index: java/engine/org/apache/derby/impl/sql/compile/ConstantNode.java
===================================================================
--- java/engine/org/apache/derby/impl/sql/compile/ConstantNode.java	(revision 468830)
+++ java/engine/org/apache/derby/impl/sql/compile/ConstantNode.java	(working copy)
@@ -282,7 +282,11 @@
 	{
 		if (isSameNodeType(o)) {
 			ConstantNode other = (ConstantNode)o;
-			return other.getValue().compare(getValue()) == 0;
+			
+			// value can be null which represents a SQL NULL value.
+			return ( (other.getValue() == null && getValue() == null) || 
+					 (other.getValue() != null && 
+							 other.getValue().compare(getValue()) == 0) );
 		}
 		return false;
 	}
Index: java/testing/org/apache/derbyTesting/functionTests/tests/lang/groupBy.sql
===================================================================
--- java/testing/org/apache/derbyTesting/functionTests/tests/lang/groupBy.sql	(revision 468830)
+++ java/testing/org/apache/derbyTesting/functionTests/tests/lang/groupBy.sql	(working copy)
@@ -372,3 +372,29 @@
 select substr(vc, 3, 4) from dt group by substr(vc, 3); 
 select substr(vc, 3) from dt group by substr(vc, 3, 4);
 drop table dt;
+create table dt(c1 varchar(10));
+insert into dt values '123 ', 'abc ', '123', 'abc';
+-- ok
+select ltrim(c1) from dt group by ltrim(c1);
+select rtrim(c1) from dt group by rtrim(c1);
+select locate(c1, 'abc') from dt group by locate(c1, 'abc');
+select locate(c1, 'abc', 1) from dt group by locate(c1, 'abc',1);
+-- expect errors
+select locate(c1, 'abc') from dt group by locate(c1, 'abc',3);
+select locate(c1, 'abc',2) from dt group by locate(c1, 'abc');
+select locate(c1, 'abc',2) from dt group by locate(c1, 'abc',3);
+drop table dt;
+
+-- DERBY-2014
+-- test NULLIF with GROUP BY expression
+create table t1 (c1 int, c2 int);
+insert into t1 values (1,1), (2,2), (2,2), (3,3), (null, null), (5,100);
+-- ok
+select nullif(c1,c1) from t1 group by nullif(c1,c1);
+select nullif(c1,c2) from t1 group by nullif(c1,c2);
+select nullif(c1,10) from t1 group by nullif(c1,10);
+select nullif(1,c1) from t1 group by nullif(1,c1);
+-- expect error
+select nullif(c1,c2) from t1 group by nullif(c2,c1);
+select nullif(c1,100) from t1 group by nullif(c1,200);
+drop table t1;
Index: java/testing/org/apache/derbyTesting/functionTests/master/groupBy.out
===================================================================
--- java/testing/org/apache/derbyTesting/functionTests/master/groupBy.out	(revision 468830)
+++ java/testing/org/apache/derbyTesting/functionTests/master/groupBy.out	(working copy)
@@ -660,4 +660,74 @@
 ERROR 42Y30: The SELECT list of a grouped query contains at least one invalid expression. If a SELECT list has a GROUP BY, the list may only contain valid grouping expressions and valid aggregate expressions.  
 ij> drop table dt;
 0 rows inserted/updated/deleted
+ij> create table dt(c1 varchar(10));
+0 rows inserted/updated/deleted
+ij> insert into dt values '123 ', 'abc ', '123', 'abc';
+4 rows inserted/updated/deleted
+ij> -- ok
+select ltrim(c1) from dt group by ltrim(c1);
+1         
+----------
+123       
+abc       
+ij> select rtrim(c1) from dt group by rtrim(c1);
+1         
+----------
+123       
+abc       
+ij> select locate(c1, 'abc') from dt group by locate(c1, 'abc');
+1          
+-----------
+0          
+1          
+ij> select locate(c1, 'abc', 1) from dt group by locate(c1, 'abc',1);
+1          
+-----------
+0          
+1          
+ij> -- expect errors
+select locate(c1, 'abc') from dt group by locate(c1, 'abc',3);
+ERROR 42Y30: The SELECT list of a grouped query contains at least one invalid expression. If a SELECT list has a GROUP BY, the list may only contain valid grouping expressions and valid aggregate expressions.  
+ij> select locate(c1, 'abc',2) from dt group by locate(c1, 'abc');
+ERROR 42Y30: The SELECT list of a grouped query contains at least one invalid expression. If a SELECT list has a GROUP BY, the list may only contain valid grouping expressions and valid aggregate expressions.  
+ij> select locate(c1, 'abc',2) from dt group by locate(c1, 'abc',3);
+ERROR 42Y30: The SELECT list of a grouped query contains at least one invalid expression. If a SELECT list has a GROUP BY, the list may only contain valid grouping expressions and valid aggregate expressions.  
+ij> drop table dt;
+0 rows inserted/updated/deleted
+ij> -- DERBY-2014
+-- test NULLIF with GROUP BY expression
+create table t1 (c1 int, c2 int);
+0 rows inserted/updated/deleted
+ij> insert into t1 values (1,1), (2,2), (2,2), (3,3), (null, null), (5,100);
+6 rows inserted/updated/deleted
+ij> -- ok
+select nullif(c1,c1) from t1 group by nullif(c1,c1);
+1          
+-----------
+NULL       
+ij> select nullif(c1,c2) from t1 group by nullif(c1,c2);
+1          
+-----------
+5          
+NULL       
+ij> select nullif(c1,10) from t1 group by nullif(c1,10);
+1          
+-----------
+1          
+2          
+3          
+5          
+NULL       
+ij> select nullif(1,c1) from t1 group by nullif(1,c1);
+1          
+-----------
+1          
+NULL       
+ij> -- expect error
+select nullif(c1,c2) from t1 group by nullif(c2,c1);
+ERROR 42Y30: The SELECT list of a grouped query contains at least one invalid expression. If a SELECT list has a GROUP BY, the list may only contain valid grouping expressions and valid aggregate expressions.  
+ij> select nullif(c1,100) from t1 group by nullif(c1,200);
+ERROR 42Y30: The SELECT list of a grouped query contains at least one invalid expression. If a SELECT list has a GROUP BY, the list may only contain valid grouping expressions and valid aggregate expressions.  
+ij> drop table t1;
+0 rows inserted/updated/deleted
 ij>