Question

我的表格TContractForm包含字段idcontract(primary key),idcntrtype(foreign key),date_begin,date_end,cost。我还有3种类型的合同：

带有字段TRentWhouseContract

的

idcontract,idclient,idpdtwhs 带有字段TRentShoppointContract

的

idcontract,idclient,idshoppoint,idshoptype 带有字段TRentEquipContract

的

idcontract,idclient,ideq,amount

idcntrtype - 合同类型。 TContractType - idcntrtype(primary key),idcntrclass(foreign key),name。 TContractClass - idcntrclass,name。

我想创建一个包含列的视图 idcontract,idclient,contract_type(name of type),contract_class(name of class),date_begin,date_end,cost。

但我的查询没有返回任何内容（我知道我在TRentWhouseContract表中有多个合同（其他表没有行）（它没有idclient因为我不知道如何从不同的表中获取相同的idclient，如果有一些表是空的。

select TCF.idcontract,
   --idclient
   TCF.date_begin,
   TCF.date_end,
   TCT.name as [type],
   TCC.name as class,
   TCF.cost
from TContractForm as TCF,
 TRentEquipContract as TREC,
 TRentShopPointContract as TRSPC,
 TRentWhouseContract as TRWC,
 TContractType as TCT,
 TContractClass as TCC
where TCF.idcontract = TREC.idcontract or TCF.idcontract = TRSPC.idcontract
  or TCF.idcontract = TRWC.idcontract and TCT.idcntrtype = TCF.idcntrtype
  and TCT.idcntrclass = TCC.idcntrclass

Answer 1

如果我理解正确，这就是我要做的事情

select TCF.idcontract,
   --idclient
   TCF.date_begin,
   TCF.date_end,
   TCT.name as [type],
   TCC.name as class,
   TCF.cost
from TContractForm as TCF
JOIN TContractType as TCT
   ON TCT.idcntrtype=TCF.idcntrtype
JOIN TContractClass as TCC
   ON TCT.idcntrclass = TCC.idcntrclass
UNION
select TCF.idcontract,
   --idclient
   TCF.date_begin,
   TCF.date_end,
   TCT.name as [type],
   TCC.name as class,
   TCF.cost
from TRentWhouseContract as TCF
JOIN TContractType as TCT
   ON TCT.idcntrtype=TCF.idcntrtype
JOIN TContractClass as TCC
   ON TCT.idcntrclass = TCC.idcntrclass
UNION
select TCF.idcontract,
   --idclient
   TCF.date_begin,
   TCF.date_end,
   TCT.name as [type],
   TCC.name as class,
   TCF.cost
from TRentShoppointContract as TCF
JOIN TContractType as TCT
   ON TCT.idcntrtype=TCF.idcntrtype
JOIN TContractClass as TCC
   ON TCT.idcntrclass = TCC.idcntrclass
UNION
select TCF.idcontract,
   --idclient
   TCF.date_begin,
   TCF.date_end,
   TCT.name as [type],
   TCC.name as class,
   TCF.cost
from TRentEquipContract as TCF
JOIN TContractType as TCT
   ON TCT.idcntrtype=TCF.idcntrtype
JOIN TContractClass as TCC
   ON TCT.idcntrclass = TCC.idcntrclass

Answer 2

如何获得idclient：

coalesce(TREC.idclient, TRSPC.idclient,TRWC.idclient) as idclient

Coalesce返回第一个非缺失值。

至于其余部分 - 我认为你应该做左外连接而不是逗号连接，因为你没有所有表中的一些记录（好吧，所有表中都没有记录！）。

select...
from TCF,TCT,TCC ... A
 left join ... TREC on A.idcontract=TREC.idcontract
 left join ... TRSPC

等

查询麻烦

2 个答案: