MySQL JOIN - 没有结果

Question

我很确定这与我选择表或联接的顺序有关，但是在我的查询中尝试了各种重新排序后，我仍然遇到 0 个结果。

有人能指出我正确的方向吗？

附件 A(返回 355 个结果):

SELECT DISTINCT
    person.person_id as "Person ID",
    CONCAT(person.last, ', ', person.first) as "Patient Name",
    person.birthday as "Birthday",
    person_ins_tie.insurance_id as "Insurance ID",
    insurance.carrier as "Carrier",
    insurance.phone as "Carrier Phone Number"
FROM
    person
        JOIN
    person_ins_tie ON person.person_id = person_ins_tie.person_id
        JOIN
    insurance ON person_ins_tie.insurance_id = insurance.insurance_id
WHERE
    insurance.carrier LIKE 'Blue%'

附件 B(返回 0 个结果/无错误):

SELECT DISTINCT
    person.person_id as 'Person ID',
    patient.display_id as 'Chart #',
    CONCAT(person.last, ', ', person.first) as 'Patient Name',
    person.birthday as 'Birthday',
    insurance.insurance_id as 'Insurance ID',
    insurance.carrier as 'Carrier',
    insurance.phone as 'Carrier Phone Number'
FROM
    person
        JOIN
    person_ins_tie ON person.person_id = person_ins_tie.person_id
        JOIN
    insurance ON person_ins_tie.insurance_id = insurance.insurance_id
        JOIN
    patient ON person.person_id = patient.person_id
WHERE
    insurance.carrier LIKE 'Blue%'

感谢您的反馈!

Answer 1

JOIN 表示INNER JOIN。

在这种情况下，当您加入 patent 表时，它会尝试从 person 表中的 person_id 中查找 person_id patent 表的 >。因此，这里唯一的可能性是在 patent 表的 person_id 列中找不到前一个连接集中的 person_id。共有 0 条记录!