+
+removing an obsolete commodity:
+
+ select * from (select * from sell union select * from buy) left outer join commods using (commodid) where commods.commodname = 'Black dye' limit 10;
+
+if that produces no output then:
+
+ begin;
+ delete from commods where commodname like 'Black dye';
+ select * from (select * from sell union select * from buy) left outer join commods using (commodid) where commods.commodname is null limit 10;
+
+and if that produces no output then:
+ commit;
+otherwise
+ rollback;
+
+=======================================
+