在一个公共表上联接,如何获得一个完整的外部联接以在另一个表上展开?

完全外部联接只能在companyID和employeeName上的TableA和TableB之间进行,因为这是一个值,如果它只存在于一个表中,则希望填充为NULL。

完全外部连接解决方案:

select Company.companyID, EmployeeNameA, EmployeeNameB
from (
    SELECT isnull(TableA.CompanyID, TableB.CompanyID) as companyID,
        TableA.EmployeeName as EmployeeNameA,
        TableB.EmployeeName as EmployeeNameB
    FROM @TableA TableA 
    FULL OUTER JOIN @TableB TableB ON TableA.EmployeeName = TableB.EmployeeName and TableA.companyID = TableB.companyID
    WHERE
     TableA.CompanyID = 12 or TableB.CompanyID = 12 
) merged
inner join @Company Company
    on merged.companyID = Company.companyID

就我个人而言,我觉得很难用完全的外部连接来思考。我的方法是:通过在受影响的表之间进行并集,在结果中找到所需的不同EmployeeNames,然后使用左联接从两个表中获取数据,从而在需要时获得null。

左连接示例:

select c.companyID, a.employeeName, b.employeeName
from  (
    select distinct employeeName, companyID
    from  (
        select a.employeeName, companyID 
        from @tableA  a
        union 
        select b.employeeName, companyID
        from @tableB b
    ) a
) z
inner join @company c
    on c.companyID = z.companyID
left join @tableA  a
    on z.companyID = a.companyID and z.employeeName = a.employeeName
left join @tableB  b
    on z.companyID = b.companyID and z.employeeName = b.employeeName
where z.companyID = 12

SELECT Company.CompanyID,
    TableA.EmployeeName,
    TableB.EmployeeName
FROM Company
LEFT OUTER JOIN TableA ON Company.CompanyID = TableA.CompanyID
LEFT OUTER JOIN TableB ON Company.CompanyID = TableB.CompanyID
WHERE (TableA.EmployeeName IS NULL OR TableB.EmployeeName IS NULL OR TableB.EmployeeName = TableA.EmployeeName)

运算后给出了测试数据和预期结果集

试试这个(问题中的表格和测试数据):

DECLARE @Company TABLE (CompanyID int)
DECLARE @TableA TABLE (EmployeeId int,CompanyId int,EmployeeName varchar(30))
DECLARE @TableB TABLE (EmployeeId int,CompanyId int,EmployeeName varchar(30))

set nocount on
INSERT INTO @Company (CompanyID) VALUES (10)
INSERT INTO @Company (CompanyID) VALUES (12)

--INSERT INTO @TableA ( EmployeeId, CompanyId, EmployeeName )--VALUES ( 2, 12, 'someone 2' )
INSERT INTO @TableA ( EmployeeId, CompanyId, EmployeeName )VALUES ( 1, 10, 'someone' )
INSERT INTO @TableA ( EmployeeId, CompanyId, EmployeeName )VALUES ( 3, 12, 'someone 3' )
INSERT INTO @TableA ( EmployeeId, CompanyId, EmployeeName )VALUES ( 3, 12, 'someone 4' )

--INSERT INTO @TableB ( EmployeeId, CompanyId, EmployeeName )--VALUES ( 3, 12, 'someone 3' )
INSERT INTO @TableB ( EmployeeId, CompanyId, EmployeeName )VALUES ( 1, 10, 'someone' )
INSERT INTO @TableB ( EmployeeId, CompanyId, EmployeeName )VALUES ( 2, 12, 'someone 2' )
INSERT INTO @TableB ( EmployeeId, CompanyId, EmployeeName )VALUES ( 3, 12, 'someone 4' )
set nocount off

SELECT coalesce(TableA.CompanyID,TableB.CompanyID) CompanyID,
    TableA.EmployeeName,
    TableB.EmployeeName
FROM @TableA TableA
FULL OUTER jOIN  @TableB TableB ON TableA.CompanyID = TableB.CompanyID AND TableB.EmployeeName = TableA.EmployeeName
WHERE coalesce(TableA.CompanyID,TableB.CompanyID) = 12

输出:

CompanyID   EmployeeName                   EmployeeName
----------- ------------------------------ ------------------------------
12          NULL                           someone 2
12          someone 3                      NULL
12          someone 4                      someone 4

(3 row(s) affected)

DECLARE @Company TABLE 
( 
    CompanyID int 
) 

INSERT INTO @Company (CompanyID) VALUES (10) 
INSERT INTO @Company (CompanyID) VALUES (12) 

DECLARE @TableA TABLE 
( 
    EmployeeId int, 
    CompanyId int, 
    EmployeeName varchar(30) 
) 

DECLARE @TableB TABLE 
( 
    EmployeeId int, 
    CompanyId int, 
    EmployeeName varchar(30) 
) 

INSERT INTO @TableA ( EmployeeId, CompanyId, EmployeeName ) 
VALUES ( 1, 10, 'someone' ) 

--INSERT INTO @TableA ( EmployeeId, CompanyId, EmployeeName ) 
--VALUES ( 2, 12, 'someone 2' ) 

INSERT INTO @TableA ( EmployeeId, CompanyId, EmployeeName ) 
VALUES ( 3, 12, 'someone 3' ) 

INSERT INTO @TableA ( EmployeeId, CompanyId, EmployeeName ) 
VALUES ( 3, 12, 'someone 4' ) 

INSERT INTO @TableB ( EmployeeId, CompanyId, EmployeeName ) 
VALUES ( 1, 10, 'someone' ) 

INSERT INTO @TableB ( EmployeeId, CompanyId, EmployeeName ) 
VALUES ( 2, 12, 'someone 2' ) 

--INSERT INTO @TableB ( EmployeeId, CompanyId, EmployeeName ) 
--VALUES ( 3, 12, 'someone 3' ) 

INSERT INTO @TableB ( EmployeeId, CompanyId, EmployeeName ) 
VALUES ( 3, 12, 'someone 4' ) 

INSERT INTO @TableB ( EmployeeId, CompanyId, EmployeeName )  
VALUES ( 3, 12, 'someone 4' )  

SELECT Company.CompanyID,  
   A.EmployeeNameTableA,  
   A.EmployeeNameTAbleB 
FROM @Company Company  
left OUTER JOIN (select TableA.EmployeeName as EmployeeNameTableA, TableB.EmployeeName as EmployeeNameTableB , 
coalesce(TableA.CompanyID,TableB.CompanyID) as CompanyID 
from @TableA TableA  
FULL OUTER JOIN @TableB TableB ON TableA.CompanyID = TableB.CompanyID and TableB.EmployeeName = TableA.EmployeeName and (tablea.companyid = 12 or tableb.companyid = 12))A ON Company.CompanyID = A.CompanyID  

WHERE Company.CompanyID = 12  

SELECT Company.CompanyID,
    TableA.EmployeeName as EmployeeNameTableA,
    TableB.EmployeeName as EmployeeNameTableB
FROM @TableA TableA 
FULL OUTER JOIN @TableB TableB ON TableA.EmployeeName = TableB.EmployeeName 
    and TableA.companyID = TableB.companyID
INNER JOIN @Company Company ON (
    Company.CompanyID = TableA.CompanyId OR Company.CompanyID = TableB.CompanyId
)
WHERE Company.CompanyID = 12

我想我最终要做的就是继续使用存储过程。