--- a/backend/doc/schema/postgresql.sql	Wed Oct 16 12:39:33 2013 +0200
+++ b/backend/doc/schema/postgresql.sql	Wed Oct 16 13:03:13 2013 +0200
@@ -34,7 +34,8 @@
     river_id int             NOT NULL REFERENCES rivers(id) ON DELETE CASCADE,
     a        NUMERIC         NOT NULL,
     b        NUMERIC,
-    UNIQUE (river_id, a, b)
+    UNIQUE (river_id, a, b),
+    CHECK (a < b)
 );
 
 
@@ -91,7 +92,7 @@
     -- Pegelnullpunkt
     datum    NUMERIC NOT NULL,
     -- Streckengueltigkeit
-    range_id int NOT NULL REFERENCES ranges (id) ON DELETE CASCADE,
+    range_id int REFERENCES ranges (id) ON DELETE CASCADE,
 
     UNIQUE (name, river_id),
     UNIQUE (official_number, river_id),
@@ -201,6 +202,7 @@
     wst_id      int NOT NULL REFERENCES wsts(id) ON DELETE CASCADE,
     name        VARCHAR(256) NOT NULL,
     description VARCHAR(256),
+    source      VARCHAR(256),
     position    int NOT NULL DEFAULT 0,
 
     time_interval_id int REFERENCES time_intervals(id),
@@ -324,7 +326,7 @@
     cross_section_line_id int             NOT NULL REFERENCES cross_section_lines(id) ON DELETE CASCADE,
     col_pos               int             NOT NULL,
     x                     NUMERIC         NOT NULL,
-    y                     NUMERIC         NOT NULL,
+    y                     NUMERIC         NOT NULL
 );
 
 -- Indices for faster access of the points