我很难从一对多表关系中提取数据。 我需要提取尚未应用“Echo”保修代码的设备合同清单。 在我的场景中,我有一份设备合同表和一份保修表。
设备合同表(以下简称EQC)的设计是:
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| EquipmentID | Contract | SerialNumber | Make | Model | Date | Customer |
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| 001 | A1 | GDS12 | GRND | GR219 | 2016-03-02 | Acme Corp|
| 002 | B1 | BQWSD | BQW | BLU22 | 2016-03-10 | Fast Lawn|
| 003 | C1 | Foo36 | Foo | Red18 | 2016-03-04 | Perfect T|
| 004 | D1 | Foo37 | Foo | Red18 | 2016-03-04 | Perfect T|
| 005 | E1 | Foo38 | Foo | Red18 | 2016-03-01 | Perfect T|
------------------------------------------------------------------------------------
保修表(以下称WAR)的设计是:
---------------------------------------------------
| SerialNum | Make | WarrantyCode | Warranty Date|
---------------------------------------------------
| GDS12 | GRND | Alpha | 2016-04-01 |
| GDS12 | GRND | Bravo | 2016-04-01 |
| GDS12 | GRND | Delta | 2016-04-01 |
| GDS12 | GRND | Charlie | 2016-04-01 |
| GDS12 | GRND | Echo | 2016-04-01 |
| BQWSD | BQW | Alpha | 2016-04-01 |
| BQWSD | BQW | Bravo | 2016-04-01 |
| BQWSD | BQW | Charlie | 2016-04-01 |
| BQWSD | BQW | Foxtrot | 2016-04-01 |
| BQWSD | BQW | Echo | 2016-04-01 |
| Foo36 | Foo | Alpha | 2016-04-01 |
| Foo36 | Foo | Bravo | 2016-04-01 |
| Foo36 | Foo | Charlie | 2016-04-01 |
| Foo36 | Foo | Hotel | 2016-04-01 |
---------------------------------------------------
我需要做的是提取尚未应用“Echo”保修代码的EQC列表。这意味着它们没有Echo记录,或者它们没有保修记录期。
我的结果集应如下所示:
------------------------------------------------------------------------------------
| EquipmentID | Contract | SerialNumber | Make | Model | Date | Customer |
------------------------------------------------------------------------------------
| 003 | C1 | Foo36 | Foo | Red18 | 2016-03-04 | Perfect T|
| 004 | D1 | Foo37 | Foo | Red18 | 2016-03-04 | Perfect T|
| 005 | E1 | Foo38 | Foo | Red18 | 2016-03-01 | Perfect T|
------------------------------------------------------------------------------------
(GDS12& BQWSD因为已应用Echo WarrantyCode而被删除。)
我的查询是:
SELECT EQC.EquipmentID
,EQC.Contract
,EQC.SerialNumber
,EQC.Make
,EQC.Model
,EQC.DATE
,EQC.Customer
FROM equipment - contracts EQC
LEFT JOIN warranty WAR
ON WAR.SerialNum = EQC.SerialNumber
AND WAR.Make = EQC.Make
WHERE WAR.WarrantyCode is null
OR WAR.WarrantyCode <> 'Echo'
结果集看起来像这样:
------------------------------------------------------------------------------------
| EquipmentID | Contract | SerialNumber | Make | Model | Date | Customer |
------------------------------------------------------------------------------------
| 001 | A1 | GDS12 | GRND | GR219 | 2016-03-02 | Acme Corp|
| 001 | A1 | GDS12 | GRND | GR219 | 2016-03-02 | Acme Corp|
| 001 | A1 | GDS12 | GRND | GR219 | 2016-03-02 | Acme Corp|
| 001 | A1 | GDS12 | GRND | GR219 | 2016-03-02 | Acme Corp|
| 002 | B1 | BQWSD | BQW | BLU22 | 2016-03-10 | Fast Lawn|
| 002 | B1 | BQWSD | BQW | BLU22 | 2016-03-10 | Fast Lawn|
| 002 | B1 | BQWSD | BQW | BLU22 | 2016-03-10 | Fast Lawn|
| 002 | B1 | BQWSD | BQW | BLU22 | 2016-03-10 | Fast Lawn|
| 003 | C1 | Foo36 | Foo | Red18 | 2016-03-04 | Perfect T|
| 003 | C1 | Foo36 | Foo | Red18 | 2016-03-04 | Perfect T|
| 003 | C1 | Foo36 | Foo | Red18 | 2016-03-04 | Perfect T|
| 003 | C1 | Foo36 | Foo | Red18 | 2016-03-04 | Perfect T|
| 004 | D1 | Foo37 | Foo | Red18 | 2016-03-04 | Perfect T|
| 005 | E1 | Foo38 | Foo | Red18 | 2016-03-01 | Perfect T|
------------------------------------------------------------------------------------
答案 0 :(得分:3)
您希望不存在的EQC 是Echo WAR。或者换言之:您希望EQC
select *
from equipment eqc
where not exists
(
select *
from warranty war
where war.serialnum = eqc.serialnumber
and war.make = eqc.make
and war.warrantycode = 'Echo'
);
或者:
select *
from equipment
where (serialnumber, make) not in
(
select serialnum, make
from warranty
where warrantycode = 'Echo'
);
更新:但是,我不确定SQL Server是否支持IN子句中的元组,如上所示。它是一个很棒的功能,可以让查询真正具有可读性,但不幸的是,有些DBMS不支持这种语法。