使用案例语句作为枢轴 - DB2 SQL

Question

我想要一份汽车运输车清单，拖车设备数量列在不同的栏目中。 我使用case语句对不同的设备类型进行分类，但是我得到了多次返回，而不是每个运营商看到一次返回。

我试过ROW OVER（）并得到相同的结果。

SELECT C.ECP_CARRIER_IDENT_ID AS ECP_ID, C.CARRIER_NM, C.MC_NB, C.DOT_NB,
(CASE WHEN E.EQUIPMENT_TYPE_CD = 'TR' THEN E.EQUIPMENT_CT END) AS TRACTORS,
(CASE WHEN E.EQUIPMENT_TYPE_CD = 'SV' THEN E.EQUIPMENT_CT END) AS VAN_TRLS,
(CASE WHEN E.EQUIPMENT_TYPE_CD = 'FT' THEN E.EQUIPMENT_CT END) AS FLATBEDS
FROM ECP_CARRIER C
JOIN ECP_CARRIER_EQUIPMENT E ON C.ECP_CARRIER_IDENT_ID = E.ECP_CARRIER_ID
WHERE CERTIFIED_FG = 1
GROUP BY C.ECP_CARRIER_IDENT_ID, C.CARRIER_NM, C.MC_NB, C.DOT_NB,
E.EQUIPMENT_TYPE_CD, E.EQUIPMENT_CT

我希望一切都在一排，但这是我得到的结果

ECP_NB   CARRIER_NM     MC_NB    DOT_NB  TRACTORS VAN_TRLS   FLATBEDS
 1234   Bob's Trucking   606066     66    10               
 1234   Bob's Trucking   606066     66              12

Answer 1

使用聚合函数并group by以下方式修复group by ：

SELECT C.ECP_CARRIER_IDENT_ID AS ECP_ID, C.CARRIER_NM, C.MC_NB, C.DOT_NB,
       MAX(CASE WHEN E.EQUIPMENT_TYPE_CD = 'TR' THEN E.EQUIPMENT_CT END) AS TRACTORS,
       MAX(CASE WHEN E.EQUIPMENT_TYPE_CD = 'SV' THEN E.EQUIPMENT_CT END) AS VAN_TRLS,
       MAX(CASE WHEN E.EQUIPMENT_TYPE_CD = 'FT' THEN E.EQUIPMENT_CT END) AS FLATBEDS
FROM ECP_CARRIER C JOIN
     ECP_CARRIER_EQUIPMENT E
     ON C.ECP_CARRIER_IDENT_ID = E.ECP_CARRIER_ID
WHERE CERTIFIED_FG = 1
GROUP BY C.ECP_CARRIER_IDENT_ID, C.CARRIER_NM, C.MC_NB, C.DOT_NB;

GROUP BY的键组合应定义结果集中所需的每一行。 您不需要E.EQUIPMENT_TYPE_CD （例如）的单独行，因此它不应该在GROUP BY 。