ปีใดมีชั้นรถไฟ 250?ไม่จำเป็นต้องใช้ตารางทั้งหมด
Which year has a railway class of 250?It is not neccessary to use all the tables.
 table_5679:  "Gauge" [ text]  "Railway" [ text]  "Class" [ text]  "Year" [ text]  "Builder" [ text] 
SELECT "Year" FROM table_5679 WHERE "Class" = '250'