php sql报错1054 in sql语句拼接 报错

1054:Unknown column 'a.first_letter' in 'where clause'

但数据表是有first_letter这个字段的

[ SQL语句 ] : SELECT a.id AS vod_id, a.classid AS vod_classid, a.name AS vod_name, a.pic_url AS vod_pic_url, a.definition AS vod_definition, a.movie_type AS vod_movie_type, b.price AS vod_price, c.pay_flag AS vod_pay_flag FROM vod AS a LEFT JOIN vod_price AS b ON b.vod_id = a.id LEFT JOIN vod_pay_log AS c ON c.pay_vod_id = a.id AND c.checkin_id = ''WHERE a.status = 1 AND a.classid =1 AND a.first_letter like 'A%' ORDER BY a.sort, a.id DESC