Question

我正在尝试通过将表Customer与已经加入的BuyVehicle＆amp;表结合起来获得一对匹配列。我给别名't'的车辆。如果我在第一行分配了别名，那么p1.SSN和我如何假设p2.SSN将跟随一个未知列？

SELECT p1.SSN, p2.SSN FROM Customer AS p1, Customer AS p2 
INNER JOIN (SELECT BVSSN, BVVin, Vin FROM CarPurchase INNER JOIN Car ON BVVin = Vin) 
AS t ON p1.SSN = BVSSN & p2.SSN = BVSSN
WHERE p1.SSN < p2.SSN AND //matching columns comparisons yet to be added;

ERROR 1054（42S22）：'on clause'中未知列'p1.SSN'

Answer 1

问题在于混合不同类型的连接。 MySQL无法识别p1表，因为它不是“连接”的一部分。以下内容应解决此问题：

SELECT p1.SSN, p2.SSN
FROM Customer AS p1 cross join
     Customer AS p2 INNER JOIN
     (SELECT BVSSN, BVVin, Vin
      FROM CarPurchase INNER JOIN
           Car
           ON BVVin = Vin
    ) AS t
    ON p1.SSN = BVSSN and p2.SSN = BVSSN
WHERE p1.SSN < p2.SSN AND //matching columns comparisons yet to be added;

实际上，您应该将WHERE子句移到ON子句中：

SELECT p1.SSN, p2.SSN
FROM Customer AS p1 join
     Customer AS p2 
     on  p1.SSN < p2.SS INNER JOIN
     (SELECT BVSSN, BVVin, Vin
      FROM CarPurchase INNER JOIN
           Car
           ON BVVin = Vin
    ) AS t
    ON p1.SSN = BVSSN and p2.SSN = BVSSN

Answer 2

什么是＆amp; - 没有这样的SQL ..改为AND
这是不正确的选择BVSSN，BVVin，Vin来自CarPurchase INNER JOIN Car ON BVVin = Vin

选择CarPurchase.BVSSN，Car.BVVin，Car.Vin来自CarPurchase INNER JOIN Car ON CarPurchase.BVVin = Car.Vin

否则使用alises

多个连接的on子句中的未知列

2 个答案: