Column 'is_valid' in where clause is ambiguous

某列 字段 所属模糊不清

例子：

SELECTa.class_id AS "classInfo.id",                 ci.class_name AS "classInfo.className"FROM class_student_info aLEFT JOIN class_info ci ON a.class_id = ci.class_idWHEREis_valid=0 此处应说明该字段 是哪张表的

               and a.student_id = '1'

改为：

SELECTa.class_id AS "classInfo.id",                ci.class_name AS "classInfo.className"FROM class_student_info aLEFT JOIN class_info ci ON a.class_id = ci.class_idWHEREa.is_valid=0       and a.student_id = '1'