question: What is the sum of number with type 0-4-4 forney locomotive, number smaller than 20 and works number of 1251?
answer: SELECT COUNT(date) FROM table_name_37 WHERE type = "0-4-4 forney locomotive" AND number < 20 AND works_number = 1251
context: CREATE TABLE table_name_37 (date VARCHAR, works_number VARCHAR, type VARCHAR, number VARCHAR)