Question

我有3个带有这些列的表：

ITV2_HIST_DEFECTOS_INSPECCION：（约500行）

C_ESTACION_ID (FK)
N_ANNO
C_INSPECCION_ID (FK)
C_SECCION_ID
C_DEFECTO_ID   (PK)
C_DEFECTO
C_CALIFICACION
U_CREACION
F_CREACION
U_MODIF
F_MODIF
N_ORDEN

ITV2_HIST_INSPECCIONES （约400行）

C_ESTACION_ID (FK)
N_ANNO
C_INSPECCION_ID (PK)
C_VEHICULO_ID (FK)
N_FASE
N_KILOMETROS
N_HORAS
C_RESULTADO
C_TIPO_INSPECC_ID (FK)
C_TIPO_INSPECCION

ITV2_HIST_VEHICULOS （约500行）

C_VEHICULO_ID (PK)
F_CAMBIO
N_BASTIDOR
A_MATRICULA
A_MARCA
A_MODELO
C_CLASIF_VEH_CONS_ID (FK)
C_CLASIF_VEH_USO_ID (FK)
C_CATEGORIA_ID (FK)
A_TIPO_VEHICULO

我尝试将3个表与此查询相关联：

 SELECT         
    INSP.C_ESTACION_ID AS ESTACION,
    INSP.C_RESULTADO AS RESULTADO,
    INSP.C_VEHICULO_ID AS C_VEHICULO_ID,
    VEHI.A_MATRICULA AS MATRICULA                            
    FROM 
    ITV2_HIST_DEFECTOS_INSPECCION DEF,
    ITV2_HIST_INSPECCIONES INSP, 
    ITV2_HIST_VEHICULOS VEHI
    WHERE               
    DEF.C_INSPECCION_ID=INSP.C_INSPECCION_ID 
    AND DEF.C_ESTACION_ID= INSP.C_ESTACION_ID
    AND INSP.C_VEHICULO_ID=VEHI.C_VEHICULO_ID

但是我收到100.000个结果。错误在哪里？

Answer 1

没有其他信息，这很难说，但是您的逻辑看起来很正确：ITV2_HIST_VEHICULOS 1：n ITV2_HIST_INSPECCIONES 1：n ITV2_HIST_DEFECTOS_INSPECCION，这应该返回不超过500行的内容。缺陷表。

添加DISTINCT可能会为您带来正确的结果，但是仍然存在错误。

由于您不返回缺陷详细信息，因此只想了解在检查过程中发现缺陷的车辆：

 SELECT         
    INSP.C_ESTACION_ID AS ESTACION,
    INSP.C_RESULTADO AS RESULTADO,
    INSP.C_VEHICULO_ID AS C_VEHICULO_ID,
    VEHI.A_MATRICULA AS MATRICULA                            
 FROM ITV2_HIST_VEHICULOS VEHI
 JOIN ITV2_HIST_INSPECCIONES INSP
   ON INSP.C_VEHICULO_ID=VEHI.C_VEHICULO_ID 
 WHERE EXISTS
  ( -- any defects recorded for this inspection?
    SELECT * 
    FROM ITV2_HIST_DEFECTOS_INSPECCION DEF
    WHERE DEF.C_INSPECCION_ID=INSP.C_INSPECCION_ID 
      AND DEF.C_ESTACION_ID= INSP.C_ESTACION_ID
  )

编辑：

由于同一辆车有多行，因此需要在加入之前应用DISTINCT：

 SELECT         
    INSP.C_ESTACION_ID AS ESTACION,
    INSP.C_RESULTADO AS RESULTADO,
    INSP.C_VEHICULO_ID AS C_VEHICULO_ID,
    VEHI.A_MATRICULA AS MATRICULA                            
 FROM ITV2_HIST_INSPECCIONES INSP
 JOIN
   ( -- hopefully there's only one A_MATRICULA per C_VEHICULO_ID
     -- otherwise switch to aggregation
     -- SELECT C_VEHICULO_ID, MAX(A_MATRICULA)
     -- FROM ITV2_HIST_VEHICULOS
     -- GROUP BY C_VEHICULO_ID
     SELECT DISTINCT C_VEHICULO_ID, A_MATRICULA
     FROM ITV2_HIST_VEHICULOS
   ) VEHI
 ON INSP.C_VEHICULO_ID=VEHI.C_VEHICULO_ID 
 WHERE EXISTS
  ( -- any defects recorded for this inspection?
    SELECT * 
    FROM ITV2_HIST_DEFECTOS_INSPECCION DEF
    WHERE DEF.C_INSPECCION_ID=INSP.C_INSPECCION_ID 
      AND DEF.C_ESTACION_ID= INSP.C_ESTACION_ID
  )

如何将这三个表与WHERE子句联系起来？

1 个答案: