refactoring #19: rename fixture files

resources/sql/functions/helpers/random_between.sql

@@ -0,0 +1,7 @@
+CREATE OR REPLACE FUNCTION random_between(low INT ,high INT)
+    RETURNS INT AS
+$$
+BEGIN
+    RETURN floor(random()* (high-low + 1) + low);
+END;
+$$ language 'plpgsql' STRICT;