Added migration script for nd_fact table.

chado/migrations/V1.3.3.010__add_environmental_fact_table.sql

@@ -0,0 +1,14 @@
+-- Adds a new "nd_fact" table to store environmental data.
+CREATE TABLE nd_fact(
+    nd_fact_id BIGSERIAL PRIMARY KEY NOT NULL,
+    nd_geolocation_id BIGINT NOT NULL REFERENCES nd_geolocation (nd_geolocation_id) ON DELETE CASCADE INITIALLY DEFERRED,
+    type_id BIGINT NOT NULL REFERENCES cvterm (cvterm_id) ON DELETE CASCADE INITIALLY DEFERRED,
+    timecaptured TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    value TEXT NULL,
+    CONSTRAINT nd_fact_c1 UNIQUE (nd_geolocation_id, type_id, timecaptured)
+  );
+CREATE INDEX nd_fact_idx1 ON nd_fact (nd_geolocation_id);
+CREATE INDEX nd_fact_idx2 ON nd_fact (timecaptured);
+
+COMMENT ON TABLE nd_fact IS 'The fact table contains facts (temparture, weather condition,...) at a given time for a given geolocation.';
+COMMENT ON COLUMN nd_fact.value IS 'The value can be NULL if the type_id is self-explicit. For instance, if the type_id term is "sunny day", there is no need for a value.';