sql - ORA-01427 单行子查询返回多于一行

Question

我遇到了 Oracle SQL 的问题，错误是： ORA-01427 单行子查询返回多于一行 我试图找到至少有一辆手动
变速箱车辆的位置，其里程低于任何豪华车那个位置。

这是我的桌子

VID          MILEAGE         LOCATION        VSIZE        TRANSMISSION
----------------------------------------------------------------------
V-101       70               AHMD            COMPACT      AUTOMATIC
V-102       50               SURAT           COMPACT      AUTOMATIC
V-103       10               AHMD            MID-SIZE     MANUAL
V-104       30               AHMD            MID-SIZE     AUTOMATIC
V-105       15               VADODARA        FULL-SIZE    AUTOMATIC
V-106       20               AHMD            LUXURY       AUTOMATIC
V-107       50               AHMD            LUXURY       MANUAL

这是我的查询：

SELECT location, transmission, mileage FROM vehicles_workshop 
  WHERE transmission = 'MANUAL' AND mileage = 
      ( SELECT DISTINCT mileage FROM vehicles_workshop WHERE mileage < 
          (SELECT MAX(mileage) FROM vehicles_workshop WHERE vsize = 'LUXURY')
      );

Answer 1

IN而不是在子查询之前使用等于运算符

SELECT location, transmission, mileage FROM vehicles_workshop 
  WHERE transmission = 'MANUAL' AND mileage IN
      ( SELECT DISTINCT mileage FROM vehicles_workshop WHERE mileage < 
          (SELECT MAX(mileage) FROM vehicles_workshop WHERE vsize = 'LUXURY')
      );

您用于比较里程的子查询返回多个值，但等于运算符只能比较单个值，因此会引发错误。

Answer 2

SELECT location, transmission, mileage 
FROM vehicles_workshop t1
WHERE transmission = 'MANUAL'         --manual transmission
  AND EXISTS
      ( SELECT *
        FROM vehicles_workshop t2 
        WHERE vsize = 'LUXURY'        --luxury vehicle
        AND t2.location = t1.location --same location
        AND t2.mileage  > t1.mileage) --higher mileage
      ;