SQL Server - 如何将值映射到主表

Question

我有这个主表：

tblMain
-----------------------------------------------
|ClientNo|Country1|Country2|Country3|Agreement|
|--------+--------+--------+--------+---------|
|111123  |SG      |TH      |PH      |OA1      |
|111222  |PH      |MY      |JP      |OA2      |
|323211  |MY      |SG      |PH      |OA3      |
-----------------------------------------------

我有这些映射表：

tblCountry
-------------------------
|CountryCode|CountryName|
|-----------+-----------|
|SG         |Singapore  |
|MY         |Malaysia   |
|PH         |Philippines|
|TH         |Thailand   |
|JP         |Japan      |
-------------------------

tblAgreement
--------------------
|ACode|ADescription|
|-----+------------|
|OA1  |Agreement1  |
|OA2  |Agreement2  |
|OA3  |Agreement3  |
--------------------

我需要实现的只是返回主表，而不是代码，我需要映射的名称/描述。 所以对于我的例子，它应该是这样的：

-------------------------------------------------------
|ClientNo|Country1   |Country2 |Country3   |Agreement |
|--------+-----------+---------+-----------+--------- |
|111123  |Singapore  |Thailand |Philippines|Agreement1|
|111222  |Philippines|Malaysia |Japan      |Agreement2|
|323211  |Malaysia   |Singapore|Philippines|Agreement3|
-------------------------------------------------------

你能帮我解决一下这个问题吗？提前谢谢

Answer 1

在select语句中使用join而不是sub查询很好。请参阅以下解决方案。

Select 
   Main.ClientNo As ClientNo, 
   CountryA.CountryName, 
   CountryB.CountryName, 
   CountryC.CountryName, 
   A.ADescription As Aggrement
From tblMain AS Main
INNER JOIN tblCountry AS CountryA ON CountryA.CountryCode = Main.Country1
INNER JOIN tblCountry AS CountryB ON CountryB.CountryCode = Main.Country2
INNER JOIN tblCountry AS CountryC ON CountryC.CountryCode = Main.Country3
INNER JOIN tblAgreement A ON Main.Agreement = A.Acode;

Answer 2

Select 
    Main.ClientNum As ClientNo,
    (Select CountryName From tblCountry Where CountryCode = Main.Country1) As Country1,
    (Select CountryName From tblCountry Where CountryCode = Main.Country2) As Country2,
    (Select CountryName From tblCountry Where CountryCode = Main.Country3) As Country3,
    A.Adescrition As Aggrement
From tblMain Main
Inner Join tblAgreement A
On Main.Aggrement = A.Acode;