查询没有返回行

Question

我正在尝试编写一个查询，对于任何预定的事件， 显示事件的详细信息，选择的客户和所有的详细信息 所需的设备。设备可以是内部设备或租用设备。内部设备和租用设备是数据库中的两个不同表。对于活动信息和客户信息，将有内部设备和租用设备。

我编写的查询使用联合技术。查询返回“没有返回行”，即使表中有明确的信息，如下图所示。

我已经使用 AS 函数重命名了两个表中的不同列，并将额外的列（例如租用设备的租金）设为 null。有人可以帮忙吗？

这是我的代码

COLUMN E_ID FORMAT A7
COLUMN E_NAME FORMAT A35
COLUMN E_STIME FORMAT A21
COLUMN E_FTIME FORMAT A21
COLUMN E_COST FORMAT 99999.99
COLUMN ET_ET_ID FORMAT A5
COLUMN ET_DESC FORMAT A10
COLUMN V_V_ID FORMAT A5
COLUMN V_NAME FORMAT A10
COLUMN C_C_ID FORMAT A5
COLUMN C_FNAME FORMAT A10
COLUMN C_LNAME FORMAT A7
COLUMN C_ORG FORMAT A20
COLUMN C_CNUM FORMAT 9999999
COLUMN EQ_ID FORMAT A5
COLUMN EQ_DESC FORMAT A30
COLUMN EQ_TYPE FORMAT A15
COLUMN EQ_AMT FORMAT A3
COLUMN RENT_FEE FORMAT 9999.99
COLUMN SU_NAME FORMAT A35
BREAK ON E_ID ON E_NAME ON C_C_ID ON C_FNAME ON C_LNAME ON C_ORG ON C_CNUM ON E_STIME ON E_FTIME ON E_COST ON ET_ET_ID ON ET_DESC ON V_V_ID ON V_NAME
SELECT E_ID, E_NAME, EVENT.C_C_ID ,C_FNAME, C_LNAME, C_ORG, C_CNUM, E_STIME, E_FTIME, E_COST, EVENT.ET_ET_ID, EVENTTYPE.ET_DESC, EVENT.V_V_ID, VENUE.V_NAME, INEQUIPMENT.IE_ID AS EQ_ID, INEQUIPMENT.IE_DESC AS EQ_DESC, INEQUIPMENT.IE_TYPE AS EQ_TYPE, EVENT_INEQUIPMENT.IE_AMT AS EQ_AMT, NULL AS RENT_FEE, NULL AS SU_NAME
FROM CUSTOMER, EVENT, EVENT_INEQUIPMENT, INEQUIPMENT, VENUE, EVENTTYPE
WHERE EVENT.E_ID = 'E000001'
AND EVENT.V_V_ID = VENUE.V_ID
AND EVENT.ET_ET_ID = EVENTTYPE.ET_ID
AND EVENT.C_C_ID = CUSTOMER.C_ID
AND EVENT.E_ID = EVENT_INEQUIPMENT.IE_IE_ID
AND EVENT_INEQUIPMENT.IE_IE_ID = INEQUIPMENT.IE_ID
UNION ALL
SELECT E_ID, E_NAME, EVENT.C_C_ID ,C_FNAME, C_LNAME, C_ORG, C_CNUM, E_STIME, E_FTIME, E_COST, EVENT.ET_ET_ID, EVENTTYPE.ET_DESC, EVENT.V_V_ID, VENUE.V_NAME, EXEQUIPMENT.XE_ID AS EQ_ID, EXEQUIPMENT.XE_DESC AS EQ_DESC, EXEQUIPMENT.XE_TYPE AS EQ_TYPE, EVENT_EXEQUIPMENT.XE_AMT AS EQ_AMT, EXEQUIPMENT.R_FEE AS RENT_FEE, SUPPLIER.SU_NAME AS SU_NAME
FROM CUSTOMER, EVENT, EVENT_EXEQUIPMENT, EXEQUIPMENT, SUPPLIER, VENUE, EVENTTYPE
WHERE EVENT.E_ID = 'E000001'
AND EVENT.V_V_ID = VENUE.V_ID
AND EVENT.ET_ET_ID = EVENTTYPE.ET_ID
AND EVENT.C_C_ID = CUSTOMER.C_ID
AND EVENT.E_ID = EVENT_EXEQUIPMENT.XE_XE_ID
AND EVENT_EXEQUIPMENT.XE_XE_ID = EXEQUIPMENT.XE_ID
AND EXEQUIPMENT.SU_SU_ID = SUPPLIER.SU_ID;

您可以从图像中清楚地看到表格中包含 E_ID = E000001 的数据

Answer 1

您正在执行一系列内部连接。这意味着，对于连接在一起的每个表，您只请求根据连接条件出现在两个表中的行。因此，如果您没有从主查询中返回任何行，那么您的表中某处的数据与您的特定 e_id 的连接条件不匹配。

首先，我将使用 ANSI 连接语法重写您的查询，如下所示：

SELECT e_id,
       e_name,
       event.c_c_id,
       c_fname,
       c_lname,
       c_org,
       c_cnum,
       e_stime,
       e_ftime,
       e_cost,
       event.et_et_id,
       eventtype.et_desc,
       event.v_v_id,
       venue.v_name,
       inequipment.ie_id        AS eq_id,
       inequipment.ie_desc      AS eq_desc,
       inequipment.ie_type      AS eq_type,
       event_inequipment.ie_amt AS eq_amt,
       NULL                     AS rent_fee,
       NULL                     AS su_name
FROM   event
       INNER JOIN customer ON event.c_c_id = customer.c_id
       INNER JOIN event_inequipment ON event.e_id = event_inequipment.ie_ie_id
       INNER JOIN inequipment ON event_inequipment.ie_ie_id = inequipment.ie_id
       INNER JOIN venue ON event.v_v_id = venue.v_id
       INNER JOIN eventtype ON event.et_et_id = eventtype.et_id
WHERE  event.e_id = 'E000001'
UNION ALL
SELECT e_id,
       e_name,
       event.c_c_id,
       c_fname,
       c_lname,
       c_org,
       c_cnum,
       e_stime,
       e_ftime,
       e_cost,
       event.et_et_id,
       eventtype.et_desc,
       event.v_v_id,
       venue.v_name,
       exequipment.xe_id        AS eq_id,
       exequipment.xe_desc      AS eq_desc,
       exequipment.xe_type      AS eq_type,
       event_exequipment.xe_amt AS eq_amt,
       exequipment.r_fee        AS rent_fee,
       supplier.su_name         AS su_name
FROM   event
       INNER JOIN customer ON event.c_c_id = customer.c_id
       INNER JOIN event_exequipment ON event.e_id = event_exequipment.xe_xe_id
       INNER JOIN exequipment ON event_exequipment.xe_xe_id = exequipment.xe_id
       INNER JOIN supplier ON exequipment.su_su_id = supplier.su_id;
       INNER JOIN venue ON event.v_v_id = venue.v_id
       INNER JOIN eventtype ON event.et_et_id = eventtype.et_id
WHERE  event.e_id = 'E000001';

完成此操作后，您可以轻松地将连接转换为左外连接或简单地将它们完全注释掉，以便诊断哪些连接没有返回任何行。

对于这样的查询，通常可以从基本表开始，然后逐个添加连接，直到找出问题所在。