diff --git a/api/__init__.py b/api/__init__.py
index 737d03e..71a3948 100644
--- a/api/__init__.py
+++ b/api/__init__.py
@@ -38,4 +38,6 @@ from .s6_pumps import get_pump_schema, add_pump, get_pump, set_pump, delete_pump
 from .s7_valves import VALVES_TYPE_PRV, VALVES_TYPE_PSV, VALVES_TYPE_PBV, VALVES_TYPE_FCV, VALVES_TYPE_TCV, VALVES_TYPE_GPV
 from .s7_valves import get_valve_schema, add_valve, get_valve, set_valve, delete_valve
 
+from .s9_demands import get_demand_schema, get_demand, set_demand
+
 from .s24_coordinates import get_node_coord
diff --git a/api/operation.py b/api/operation.py
index 79a3a3b..d418874 100644
--- a/api/operation.py
+++ b/api/operation.py
@@ -51,6 +51,12 @@ def read(name: str, sql: str) -> Row:
         return row
 
 
+def read_all(name: str, sql: str) -> list[Row]:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(sql)
+        return cur.fetchall()
+
+
 def write(name: str, sql: str) -> None:
     with conn[name].cursor() as cur:
         cur.execute(sql)
diff --git a/api/s9_demands.py b/api/s9_demands.py
new file mode 100644
index 0000000..01b798b
--- /dev/null
+++ b/api/s9_demands.py
@@ -0,0 +1,56 @@
+from .operation import *
+from .s0_base import *
+
+
+def get_demand_schema(name: str) -> dict[str, dict[str, Any]]:
+    return { 'junction' : {'type': 'str'  , 'optional': False , 'readonly': True },
+             'demands'  : {'type': 'list' , 'optional': False , 'readonly': False, 
+                           'element': { 'demand'  : {'type': 'float' , 'optional': False , 'readonly': False }, 
+                                        'patten'  : {'type': 'str'   , 'optional': True ,  'readonly': False },
+                                        'category': {'type': 'str'   , 'optional': True ,  'readonly': False }}}}
+
+
+def get_demand(name: str, junction: str) -> dict[str, Any]:
+    des = read_all(name, f"select * from demands where junction = '{junction}'")
+    ds = []
+    for r in des:
+        d = {}
+        d['demand'] = float(r['demand'])
+        d['pattern'] = str(r['pattern']) if r['pattern'] != None else None
+        d['category'] = str(r['category']) if r['category'] != None else None
+        ds.append(d)
+    return { 'junction': junction, 'demands': ds }
+
+# { 'operation': 'update', 'type': 'demand', 'junction': 'j1', 'demands': [{'demand': 0.0, 'patten': None, 'category': None}] }
+def set_demand(name: str, cs: ChangeSet) -> ChangeSet:
+    junction = cs.operations[0]['junction']
+    old = get_demand(name, junction)
+    new = { 'junction': junction, 'demands': [] }
+
+    f_junction = f"'{junction}'"
+
+    redo_sql = f"delete from demands where junction = {f_junction};"
+    for r in cs.operations[0]['demands']:
+        demand = float(r['demand'])
+        pattern = str(r['pattern']) if 'pattern' in r and r['pattern'] != None else None
+        category = str(r['category']) if 'category' in r and r['category'] != None else None
+        f_demand = demand
+        f_pattern = f"'{pattern}'" if pattern != None else 'null'
+        f_category = f"'{category}'" if category != None else 'null'
+        redo_sql += f"\ninsert into demands (junction, demand, pattern, category) values ({f_junction}, {f_demand}, {f_pattern}, {f_category});"
+        new['demands'].append({ 'demand': demand, 'pattern': pattern, 'category': category })
+
+    undo_sql = f"delete from demands where junction = {f_junction};"
+    for r in old['demands']:
+        demand = float(r['demand'])
+        pattern = str(r['pattern'])
+        category = str(r['category'])
+        f_demand = demand
+        f_pattern = f"'{pattern}'" if pattern != None else 'null'
+        f_category = f"'{category}'" if category != None else 'null'
+        undo_sql += f"\ninsert into demands (junction, demand, pattern, category) values ({f_junction}, {f_demand}, {f_pattern}, {f_category});"
+    
+    redo_cs = g_update_prefix | { 'type': 'demand' } | new
+    undo_cs = g_update_prefix | { 'type': 'demand' } | old
+
+    return execute_command(name, redo_sql, undo_sql, redo_cs, undo_cs)
diff --git a/script/sql/create/9.demands.sql b/script/sql/create/9.demands.sql
index 6e4b2a5..d2d2943 100644
--- a/script/sql/create/9.demands.sql
+++ b/script/sql/create/9.demands.sql
@@ -5,5 +5,5 @@ create table demands
   junction varchar(32) references junctions(id) not null
 , demand numeric not null
 , pattern varchar(32) references _pattern(id)
-, category text not null
+, category text
 );
diff --git a/test_tjnetwork.py b/test_tjnetwork.py
index 34c48e1..a0d88aa 100644
--- a/test_tjnetwork.py
+++ b/test_tjnetwork.py
@@ -1174,6 +1174,72 @@ class TestApi:
         self.leave(p)
 
 
+    def test_demand(self):
+        p = 'test_demand'
+        self.enter(p)
+
+        add_junction(p, ChangeSet({'id': 'j1', 'x': 0.0, 'y': 10.0, 'elevation': 20.0}))
+        assert is_junction(p, 'j1')
+
+        set_demand(p, ChangeSet({'junction': 'j1', 'demands': [{'demand': 10.0, 'pattern': None, 'category': 'x'},
+                                                               {'demand': 20.0, 'pattern': None, 'category': None}]}))
+        d = get_demand(p, 'j1')
+        assert d['junction'] == 'j1'
+        ds = d['demands']
+        assert len(ds) == 2
+        assert ds[0]['demand'] == 10.0
+        assert ds[0]['pattern'] == None
+        assert ds[0]['category'] == 'x'
+        assert ds[1]['demand'] == 20.0
+        assert ds[1]['pattern'] == None
+        assert ds[1]['category'] == None
+
+        self.leave(p)
+
+
+    def test_demand_op(self):
+        p = 'test_demand'
+        self.enter(p)
+
+        add_junction(p, ChangeSet({'id': 'j1', 'x': 0.0, 'y': 10.0, 'elevation': 20.0}))
+        assert is_junction(p, 'j1')
+
+        cs = set_demand(p, ChangeSet({'junction': 'j1', 'demands': [{'demand': 10.0, 'pattern': None, 'category': 'x'},
+                                                                    {'demand': 20.0, 'pattern': None, 'category': None}]})).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == 'demand'
+        assert cs['junction'] == 'j1'
+        ds = cs['demands']
+        assert len(ds) == 2
+        assert ds[0]['demand'] == 10.0
+        assert ds[0]['pattern'] == None
+        assert ds[0]['category'] == 'x'
+        assert ds[1]['demand'] == 20.0
+        assert ds[1]['pattern'] == None
+        assert ds[1]['category'] == None
+
+        cs = execute_undo(p).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == 'demand'
+        assert cs['junction'] == 'j1'
+        assert len(cs['demands']) == 0
+
+        cs = execute_redo(p).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == 'demand'
+        assert cs['junction'] == 'j1'
+        ds = cs['demands']
+        assert len(ds) == 2
+        assert ds[0]['demand'] == 10.0
+        assert ds[0]['pattern'] == None
+        assert ds[0]['category'] == 'x'
+        assert ds[1]['demand'] == 20.0
+        assert ds[1]['pattern'] == None
+        assert ds[1]['category'] == None
+
+        self.leave(p)
+
+
     def test_snapshot(self):
         p = "test_snapshot"
         self.enter(p)
diff --git a/tjnetwork.py b/tjnetwork.py
index 06082be..72e193e 100644
--- a/tjnetwork.py
+++ b/tjnetwork.py
@@ -290,6 +290,21 @@ def delete_valve(name: str, cs: ChangeSet) -> ChangeSet:
     return api.delete_valve(name, cs)
 
 
+############################################################
+# demands 9.[DEMANDS]
+############################################################
+
+def get_demand_schema(name: str) -> dict[str, dict[str, Any]]:
+    return api.get_demand_schema(name)
+
+def get_demand(name: str, junction: str) -> dict[str, Any]:
+    return api.get_demand(name, junction)
+
+# { 'operation': 'update', 'type': 'demand', 'junction': 'j1', 'demands': [{'demand': 0.0, 'patten': None, 'category': None}] }
+def set_demand(name: str, cs: ChangeSet) -> ChangeSet:
+    return api.set_demand(name, cs)
+
+
 ############################################################
 # coord 24.[COORDINATES]
 ############################################################