ORA-01427单行子查询返回的行多

Question

我遇到了Oracle SQL的问题，错误是： ORA-01427单行子查询返回的行数多于我正在尝试查找具有至少一部手动车辆的位置
变速箱的行驶里程低于该位置的任何豪华车。

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

在子查询之前使用IN代替等于运算符

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')
      );

您的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
      ;