Column 'is_valid' in where clause is ambiguous

某列 字段 所属模糊不清

例子：

SELECT
a.class_id AS "classInfo.id",

                 ci.class_name AS "classInfo.className"
FROM class_student_info a
LEFT JOIN class_info ci ON a.class_id = ci.class_id
WHERE
is_valid=0 此处应说明该字段 是哪张表的

               and a.student_id = '1'

改为：

SELECT
a.class_id AS "classInfo.id",

                ci.class_name AS "classInfo.className"
FROM class_student_info a
LEFT JOIN class_info ci ON a.class_id = ci.class_id
WHERE
a.is_valid=0
       and a.student_id = '1'