SQL查询SELECT FROM 2 tables - equals返回正确的结果,但不必等于

Question

基本上,我想从customers表中获取未出现在brochure_requests表中的所有行.

SELECT *      
  FROM customers  JOIN  brochure_requests
    WHERE brochure_requests.first_name != customers.customer_first_name
    AND brochure_requests.last_name != customers.customer_last_name

当参数为=时查询有效,但是一旦我运行!=查询,程序(HeidiSQL)就会无限期挂起或直到我取消它.

Answer 1

你在brochure_requests表中没有customerID吗？

如果你这样做,你可以这样做:

select * from customers 
where customerId not in (select customerId from brochure_requests)