CREATE TABLE table_5679 ("Gauge" CLOB, "Railway" CLOB, "Class" CLOB, "Works no." CLOB, "Year" CLOB, "Builder" CLOB)

Which year has a railway class of 250?
SELECT "Year" FROM table_5679 WHERE "Class" = '250'
SELECT "Year" FROM "table_5679" WHERE "Class" = '250'