CREATE TABLE table_203_594 (id DECIMAL, "canal" TEXT, "length  ( miles ) " DECIMAL, "locks" DECIMAL, "max length  ( ft ) " DECIMAL, "width  ( ft ) " DECIMAL, "year opened" DECIMAL, "year abandoned" DECIMAL, "year restored" DECIMAL)

which was the first canal opened in scotland ?
SELECT "canal" FROM table_203_594 ORDER BY "year opened" LIMIT 1
SELECT "canal" FROM "table_203_594" ORDER BY "year opened" NULLS FIRST LIMIT 1