CREATE TABLE table_43559 ("1946 Nos" CLOB, "1947 Nos" CLOB, "Date" FLOAT, "Built at" CLOB, "LMS Nos" CLOB, "BR Nos" CLOB)

Which Built at has a Date of 1946, and a 1947 Nos of 3556/7?
SELECT "Built at" FROM table_43559 WHERE "Date" = '1946' AND "1947 Nos" = '3556/7'
SELECT "Built at" FROM "table_43559" WHERE "1947 Nos" = '3556/7' AND "Date" = '1946'