如何将表与1对多关系合并为1行记录

Question

我需要将两个表结合成一对多关系，但使用union而不成功。

我一直在尝试使用此代码

select a.equipmentid, 
a.codename, 
a.name, 
a.labelid, 
a.ACQUISITIONDATE, 
a.description 
from TBL_EQUIPMENTMST a where 
a.partofid = '57' 
union all 
select first 1 b.warrantyid, b.startdate, b.enddate from tbl_equipwarranty b 
inner join TBL_EQUIPMENTMST c 
on b.equipmentid=c.equipmentid 
where c.partofid = '57' and b.servicetype='service' order by b.warrantyid desc 
union all 
select first 1 d.warrantyid, d.startdate, d.enddate from tbl_equipwarranty d 
inner join TBL_EQUIPMENTMST e 
on d.equipmentid=e.equipmentid 
where e.partofid = '57' and d.servicetype='product' order by d.warrantyid desc 

谁能帮助我如何产生我的形象我的预期输出。我正在使用firebird作为数据库。如果你在MySQL中有一个解决方案，请告诉我，并试图找到firebird中的对手。

Answer 1

秘诀是加入tbl_equipwarranty两次 - 使用2个不同的别名。一个用于服务保修，另一个用于产品保修。您可以通过将servicetype指定为连接的一部分来完成此操作。下面使用ANSI连接，因此可能会在火鸟和MySQL的工作：

SELECT 
    a.equipmentid, 
    a.codename, 
    a.name, 
    a.labelid, 
    a.ACQUISITIONDATE, 
    a.description, 
    a.partofid, 
    w1.warrantyid as serviceidwarranty, 
    w1.startdate, 
    w1.enddate, 
    w2.warrantyid as productidwarranty, 
    w2.startdate, 
    w2.enddate 
FROM TBL_EQUIPMENTMST a 
INNER JOIN tbl_equipwarranty w1 
    ON w1.equipmentid = a.equipmentid AND w1.servicetype = 'service' 
INNER JOIN tbl_equipwarranty w2 
    ON w2.equipmentid = a.equipmentid AND w2.servicetype = 'Product' 
WHERE 
a.partofid = '57' 

Answer 2

这会给你所需的结果，只有当你有礼物表的equipmentid独特warrantyid。

SELECT 
a.equipmentid, 
a.codename, 
a.name, 
a.labelid, 
a.ACQUISITIONDATE, 
a.description, 
a.partofid, 
B.warrantyid AS serviceidwarranty, 
B.Startdate, 
B.Enddate, 
C.warrantyid AS productidwarranty, 
C.Startdate, 
C.Enddate 

FROM TBL_EQUIPMENTMST A 
LEFT OUTER JOIN tbl_equipwarranty B ON A.equipmentid=B.equipmentid AND B.Servicetype='Service' 
LEFT OUTER JOIN tbl_equipwarranty C ON A.equipmentid=C.equipmentid AND C.Servicetype='Product'