database: Add v_virtual_season

sql/v01/30.create.view.sql

@@ -5,6 +5,12 @@ FROM AT_gem g
     JOIN AT_ort o ON o.gkz = g.gkz
     JOIN AT_plz_dest p ON p.okz = o.okz;
 
+CREATE VIEW v_virtual_season AS
+SELECT year, max_kg_per_ha
+FROM season
+UNION
+SELECT strftime('%Y', date()) + 0, (SELECT max_kg_per_ha FROM season ORDER BY year DESC LIMIT 1);
+
 CREATE VIEW v_delivery AS
 SELECT p.year, p.did, p.dpnr,
        d.date, d.time, d.zwstid, d.lnr, d.lsnr,