diff --git a/src/.DS_Store b/src/.DS_Store
new file mode 100644
index 0000000..535a8dc
Binary files /dev/null and b/src/.DS_Store differ
diff --git a/src/backend/.DS_Store b/src/backend/.DS_Store
new file mode 100644
index 0000000..327792b
Binary files /dev/null and b/src/backend/.DS_Store differ
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 3bc42ba..eb42901 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -1986,6 +1986,40 @@ WinGetPartitionLocalMemory(WindowObject winobj, Size sz)
 }
 
 /*
+ * WinGetResultDatumCopy
+ *		Gets a copy of the given datum.
+ *
+ * This uses the window's per-function ByVal and TypeLen information
+ * when copying the datum.
+ */
+Datum
+WinGetResultDatumCopy(WindowObject winobj, Datum datum)
+{
+	WindowStatePerFunc perfunc;
+
+	Assert(WindowObjectIsValid(winobj));
+	perfunc = winobj->winstate->perfunc;
+	return datumCopy(datum, perfunc->resulttypeByVal, perfunc->resulttypeLen);
+}
+
+/*
+ * WinFreeResultDatumCopy
+ *		Frees a Datum previously created by WinGetResultDatumCopy.
+ *
+ * This uses the window's per-function ByVal and TypeLen information
+ * when copying the datum.
+ */
+void
+WinFreeResultDatumCopy(WindowObject winobj, Datum datum)
+{
+	WindowStatePerFunc perfunc;
+
+	Assert(WindowObjectIsValid(winobj));
+	perfunc = winobj->winstate->perfunc;
+	datumFree(datum, perfunc->resulttypeByVal, perfunc->resulttypeLen);
+}
+
+/*
  * WinGetCurrentPosition
  *		Return the current row's position (counting from 0) within the current
  *		partition.
@@ -1996,6 +2030,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 9d07f30..6dda644 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -496,6 +496,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
+				over_specification
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 
@@ -551,7 +552,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	INCLUDING INCREMENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -581,7 +582,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -615,6 +616,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  * creates these tokens when required.
  */
 %token			NULLS_FIRST NULLS_LAST WITH_TIME
+%token			RESPECT_NULLS IGNORE_NULLS
 
 
 /* Precedence: lowest to highest */
@@ -11785,7 +11787,8 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
+over_specification:
+			  OVER window_specification
 				{ $$ = $2; }
 			| OVER ColId
 				{
@@ -11800,6 +11803,18 @@ over_clause: OVER window_specification
 					n->location = @2;
 					$$ = n;
 				}
+			;
+
+over_clause: over_specification
+				{ $$ = $1; }
+			| RESPECT_NULLS over_specification
+				{ $$ = $2; }
+			| IGNORE_NULLS over_specification
+				{
+					if($2)
+						$2->frameOptions |= FRAMEOPTION_IGNORE_NULLS;
+					$$ = $2;
+				}	
 			| /*EMPTY*/
 				{ $$ = NULL; }
 		;
@@ -12765,6 +12780,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12852,6 +12868,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index b8ec790..25d09e0 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -156,6 +156,33 @@ base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, core_yyscan_t yyscanner)
 			}
 			break;
 
+		/*
+		 * Window functions can use RESPECT NULLS or IGNORE NULLS to
+		 * modify their behaviour
+		 */
+		case RESPECT:
+			cur_yylval = lvalp->core_yystype;
+			cur_yylloc = *llocp;
+			next_token = core_yylex(&(lvalp->core_yystype), llocp, yyscanner);
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = RESPECT_NULLS;
+					break;
+			}
+			break;
+		case IGNORE:
+			cur_yylval = lvalp->core_yystype;
+			cur_yylloc = *llocp;
+			next_token = core_yylex(&(lvalp->core_yystype), llocp, yyscanner);
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = IGNORE_NULLS;
+					break;
+			}
+			break;
+
 		default:
 			break;
 	}
diff --git a/src/backend/utils/.DS_Store b/src/backend/utils/.DS_Store
new file mode 100644
index 0000000..cbbea58
Binary files /dev/null and b/src/backend/utils/.DS_Store differ
diff --git a/src/backend/utils/adt/datum.c b/src/backend/utils/adt/datum.c
index 612b7ef..e72f5a9 100644
--- a/src/backend/utils/adt/datum.c
+++ b/src/backend/utils/adt/datum.c
@@ -129,7 +129,7 @@ datumCopy(Datum value, bool typByVal, int typLen)
 		realSize = datumGetSize(value, typByVal, typLen);
 
 		s = (char *) palloc(realSize);
-		memcpy(s, DatumGetPointer(value), realSize);
+		memcpy(s, 	(value), realSize);
 		res = PointerGetDatum(s);
 	}
 	return res;
@@ -144,7 +144,6 @@ datumCopy(Datum value, bool typByVal, int typLen)
  * ONLY datums created by "datumCopy" can be freed!
  *-------------------------------------------------------------------------
  */
-#ifdef NOT_USED
 void
 datumFree(Datum value, bool typByVal, int typLen)
 {
@@ -155,7 +154,6 @@ datumFree(Datum value, bool typByVal, int typLen)
 		pfree(s);
 	}
 }
-#endif
 
 /*-------------------------------------------------------------------------
  * datumIsEqual
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index 2f171ac..fea772f 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -25,6 +25,15 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * structure for IGNORE NULLS / RESPECT NULLS semantics
+ */
+typedef struct leadlag_context
+{
+	Datum		last;			/* last non-null result */
+	bool		last_isnull;
+} leadlag_context;
+
+/*
  * ntile process information
  */
 typedef struct
@@ -292,6 +301,8 @@ leadlag_common(FunctionCallInfo fcinfo,
 	Datum		result;
 	bool		isnull;
 	bool		isout;
+	bool		ignore_nulls;
+	leadlag_context* context;
 
 	if (withoffset)
 	{
@@ -322,8 +333,47 @@ leadlag_common(FunctionCallInfo fcinfo,
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
 	}
 
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
+	if(ignore_nulls)
+	{
+		/*
+		 * We'll keep the last non-null value we've seen in our per-partition chunk
+		 * of memory, so it gets cleaned up for us. 
+		 */
+		context = (leadlag_context *) 
+			WinGetPartitionLocalMemory(winobj, sizeof(leadlag_context));
 		if(isnull)
+		{
+			if(context->last != NULL)
+			{
+				/* restore the stashed copy */
+				result = context->last;
+				isnull = context->last_isnull;
+			}
+		}
+		else
+		{
+			if(context->last != NULL)
+			{
+				/* 
+				 * This step is not strictly necessary as the Datum copies are
+				 * allocated in a context that'll be discarded after this query.
+				 * However, we'd like to avoid a large memory spike during the
+				 * query (as we'd get if we kept a copy of all the non-null 
+				 * results for the duration of the query) so we'll free the
+				 * Datum copies as we go along:
+				 */
+				WinFreeResultDatumCopy(winobj, context->last);
+			}
+			context->last = WinGetResultDatumCopy(winobj, result);
+			context->last_isnull = isnull;
+		}
+	}
+
+	if (isnull)
+	{
 		PG_RETURN_NULL();
+	}
 
 	PG_RETURN_DATUM(result);
 }
diff --git a/src/include/.DS_Store b/src/include/.DS_Store
new file mode 100644
index 0000000..d5711fe
Binary files /dev/null and b/src/include/.DS_Store differ
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 2229ef0..a13c58b 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS				0x04000 /* lead/lag/nth */
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 68a13b7..2acf073 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD)
+PG_KEYWORD("ignore", IGNORE, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
+PG_KEYWORD("respect", RESPECT, UNRESERVED_KEYWORD)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD)
 PG_KEYWORD("returning", RETURNING, RESERVED_KEYWORD)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..73524ca 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
@@ -61,4 +63,7 @@ extern Datum WinGetFuncArgInFrame(WindowObject winobj, int argno,
 extern Datum WinGetFuncArgCurrent(WindowObject winobj, int argno,
 					 bool *isnull);
 
+extern Datum WinGetResultDatumCopy(WindowObject winobj, Datum datum);
+extern void WinFreeResultDatumCopy(WindowObject winobj, Datum datum);
+
 #endif   /* WINDOWAPI_H */
diff --git a/src/interfaces/.DS_Store b/src/interfaces/.DS_Store
new file mode 100644
index 0000000..c8d03e0
Binary files /dev/null and b/src/interfaces/.DS_Store differ
diff --git a/src/interfaces/ecpg/.DS_Store b/src/interfaces/ecpg/.DS_Store
new file mode 100644
index 0000000..b3e3f35
Binary files /dev/null and b/src/interfaces/ecpg/.DS_Store differ
diff --git a/src/interfaces/ecpg/preproc/parse.pl b/src/interfaces/ecpg/preproc/parse.pl
index f4b51d6..fe5dcb3 100644
--- a/src/interfaces/ecpg/preproc/parse.pl
+++ b/src/interfaces/ecpg/preproc/parse.pl
@@ -45,6 +45,8 @@ my %replace_string = (
 	'WITH_TIME'    => 'with time',
 	'NULLS_FIRST'  => 'nulls first',
 	'NULLS_LAST'   => 'nulls last',
+	'RESPECT_NULLS'  => 'respect nulls',
+	'IGNORE_NULLS'   => 'ignore nulls',
 	'TYPECAST'     => '::',
 	'DOT_DOT'      => '..',
 	'COLON_EQUALS' => ':=',);
diff --git a/src/interfaces/ecpg/preproc/parser.c b/src/interfaces/ecpg/preproc/parser.c
index 2ce9dd9..53f4167 100644
--- a/src/interfaces/ecpg/preproc/parser.c
+++ b/src/interfaces/ecpg/preproc/parser.c
@@ -121,6 +121,53 @@ filtered_base_yylex(void)
 			}
 			break;
 
+		/*
+		 * Window functions can use RESPECT NULLS or IGNORE NULLS to
+		 * modify their behaviour
+		 */
+		case RESPECT:
+			cur_yylval = base_yylval;
+			cur_yylloc = base_yylloc;
+			next_token = base_yylex();
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = RESPECT_NULLS;
+					break;
+				default:
+					/* save the lookahead token for next time */
+					lookahead_token = next_token;
+					lookahead_yylval = base_yylval;
+					lookahead_yylloc = base_yylloc;
+					have_lookahead = true;
+					/* and back up the output info to cur_token */
+					base_yylval = cur_yylval;
+					base_yylloc = cur_yylloc;
+					break;
+			}
+			break;
+		case IGNORE:
+			cur_yylval = base_yylval;
+			cur_yylloc = base_yylloc;
+			next_token = base_yylex();
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = IGNORE_NULLS;
+					break;
+				default:
+					/* save the lookahead token for next time */
+					lookahead_token = next_token;
+					lookahead_yylval = base_yylval;
+					lookahead_yylloc = base_yylloc;
+					have_lookahead = true;
+					/* and back up the output info to cur_token */
+					base_yylval = cur_yylval;
+					base_yylloc = cur_yylloc;
+					break;
+			}
+			break;
+
 		default:
 			break;
 	}
diff --git a/src/test/.DS_Store b/src/test/.DS_Store
new file mode 100644
index 0000000..7c9864e
Binary files /dev/null and b/src/test/.DS_Store differ
diff --git a/src/test/regress/.DS_Store b/src/test/regress/.DS_Store
new file mode 100644
index 0000000..a623e62
Binary files /dev/null and b/src/test/regress/.DS_Store differ
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 752c7b4..41d76a6 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    favourite_animal text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -1020,5 +1022,114 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 ERROR:  argument of ntile must be greater than zero
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 ERROR:  argument of nth_value must be greater than zero
+-- test null behaviour: (1) lags
+SELECT lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+    lag     
+------------
+ 
+ 
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+(10 rows)
+
+SELECT lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+    lag     
+------------
+ 
+ 
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+(10 rows)
+
+-- a numeric (date) column
+SELECT lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+    lag     
+------------
+ 
+ 
+ 
+ 03-05-2009
+ 09-22-2010
+ 09-22-2010
+ 09-22-2010
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT lag(favourite_animal) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+   lag   
+---------
+ 
+ frog
+ frog
+ frog
+ chicken
+ chicken
+ chicken
+ tiger
+ gorilla
+ gorilla
+(10 rows)
+
+-- (2) leads
+SELECT lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+    lead    
+------------
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+ 
+ 
+(10 rows)
+
+SELECT lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+    lead    
+------------
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+ 
+ 
+(10 rows)
+
+SELECT lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+    lead    
+------------
+ 
+ 03-05-2009
+ 09-22-2010
+ 09-22-2010
+ 09-22-2010
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..67e9a9a 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    favourite_animal text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +266,25 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- a numeric (date) column
+SELECT lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- a text column
+SELECT lag(favourite_animal) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- (2) leads
+
+SELECT lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
 -- cleanup
 DROP TABLE empsalary;