检查另一个表sql中某列的值是否存在

Question

我是SQL Server的新手。我必须将一列的值从表A复制到另一个表B中关于另一个列(JOIN)，但在复制之前，我必须检查这个值是否存在于另一个表C中。如果存在，则复制，否则返回其值不在表C中的记录。我的查询是

IF EXISTS (SELECT Branch_ID FROM ADM_Branch
INNER JOIN UBL$ on ADM_Branch.Branch_Code = UBL$.[Branch Code  ] 
 WHERE ADM_Branch.Branch_Code = [UBL$].[Branch Code] )

        UPDATE EMP_Personal
    SET Account_Number = UBL$.[Account ] , Bank_ID = 1 , Branch_ID = (select Branch_ID from ADM_Branch join UBL$ on ADM_Branch.Branch_Code = UBL$.[Branch Code  ] where EMP_Personal.Emp_ID = UBL$.[Employee ID  ])
    FROM EMP_Personal JOIN UBL$
    ON EMP_Personal.Emp_ID = UBL$.[Employee ID  ]


ELSE

    ( SELECT UBL$.[Employee ID  ],UBL$.[Name ],UBL$.[Account ],UBL$.[Branch Code  ]
    FROM UBL$) except ( SELECT UBL$.[Employee ID  ],UBL$.[Name ],UBL$.[Account ],UBL$.[Branch Code  ]
    FROM UBL$
    right join ADM_Branch on  ADM_Branch.Branch_Code = UBL$.[Branch Code  ])

Answer 1

我想下面的代码会给你一些启发，我试着保持列名不变，但你可能需要做一些修改：

UPDATE EMP
SET EMP.Account_Number = UBL.[Account ],
    EMP.Bank_ID = 1,
    EMP.Branch_ID = ADM.Branch_ID   
FROM EMP_Personal EMP
JOIN UBL$ UBL ON EMP_Personal.Emp_ID = UBL.[Employee ID  ]
JOIN ADM_Branch ADM ON ADM.Branch_Code = UBL.[Branch Code  ];

SELECT [Employee ID  ],[Name ],[Account],[Branch Code  ]
FROM UBL$ 
WHERE [Branch Code  ] NOT IN (SELECT Branch_Code FROM ADM_Branch);

Answer 2

对于条件INSERT/UPDATE/DELETE，最好使用MERGE语句。它的语法一开始并不容易，最后的语句也很长，但这是一个非常强大的工具。我建议你去学习它。在MS SQL Server 2008和更高版本中可以访问合并。

Answer 3

感谢我用这种方式做的一切；

UPDATE EMP_Personal
SET account_number = s.[Account ] , Bank_ID = 1 , Branch_ID= (select Branch_ID from ADM_Branch join UBL$ on ADM_Branch.Branch_Code = UBL$.[Branch Code  ] where EMP_Personal.Emp_ID = UBL$.[Employee ID  ])
FROM emp_personal
INNER JOIN (
SELECT UBL$.[Account ] , UBL$.[Employee ID  ]
FROM UBL$
INNER JOIN adm_branch
ON adm_branch.branch_code = UBL$.[Branch Code  ] ) as s
ON s.[Employee ID  ] = emp_personal.Emp_ID