mysql - 如何在MySQL中基于ncarpk的基础上加入三个表

我想在tour_customer，tour_provider，预订中检查ncarpk，如果有任何表有ncarpk = 7的记录，则显示结果。

select *
from tour_customer
    Left Outer join tour_provider on tour_provider.nCarPk = '7'
    Left Outer join reservation on reservation.nCarPk = '7'
where tour_customer.ncarpk = '7'

最佳答案

我会尝试

select *
from tour_customer
Left Outer join tour_provider on tour_provider.nCarPk =customer.ncarpk
Left Outer join reservation on reservation.nCarPk = customer.ncarpk
where tour_customer.ncarpk = '7'

这是进行联接的正常方法，您说出要在哪个字段上进行联接，然后添加where子句。