CREATE TABLE table_204_637 (id NUMBER, "type" CLOB, "gauge" CLOB, "railway" CLOB, "works no." CLOB, "year" CLOB, "builder" CLOB)

how many total garratts did south african railways have ?
SELECT COUNT(*) FROM table_204_637 WHERE "railway" = 'south african railways'
SELECT COUNT(*) FROM "table_204_637" WHERE "railway" = 'south african railways'