带Case / IF的SQL更新

Question

我有8位列，A1，A2，a3，a4，b1，b2，b3，b4。 所有8个都是完全独立的，并且基于这些，应该填充另一个字段。

我想用文本A，B或AB更新这个其他字段，具体取决于8列中的哪一列设置为1。

这里有几个例子; - 所有8个字段都设置为1，然后填充AB，
- 如果A3和B1设置为1，则填充AB，
- 如果A1和A3设置为1，则填充A，
- 如果B4和B2设置为1，则填充B.

因此，对于A1到B4的任何组合，应设置字段

以下是我所尝试的但它不完整但会给出一个想法;

UPDATE

来自adrianm的正确答案

UPDATE m
SET ref = ASet + BSet 
FROM contactMaster m
inner join contact c on 
m.contactid = c.contactid
 CROSS APPLY (
     SELECT CASE WHEN (c.A1 | c.A2 | c.A3 | c.A4) = 1 THEN 'C' ELSE '' END AS ASet
           ,CASE WHEN (c.B1 | c.B2 | c.B3 | c.B4) = 1 THEN 'D' ELSE '' END AS BSet
 ) AS CA1 
where ref is null

Answer 1

UPDATE ContactMaster
    SET ref = ASet + BSet 
FROM ContactMaster
     INNER JOIN Contact
          ON ContactMaster.ContactId = Contact.ContactId
     CROSS APPLY (
         SELECT CASE WHEN (Contact.A1 | Contact.A2 | Contact.A3 | Contact.A4) = 1 THEN 'A' ELSE '' END AS ASet
               ,CASE WHEN (Contact.B1 | Contact.B2 | Contact.B3 | Contact.B4) = 1 THEN 'B' ELSE '' END AS BSet
     ) AS CA1 
WHERE ContactMaster.ref IS NULL

Answer 2

IF (Select Count(*) from table where A1=1 AND A2 =1 AND a3 =1 AND a4 =1 AND b1 =1 AND b2 =1 AND b3 =1 AND b4=1 )>0
    BEGIN

    UPDATE MyTable 
    SET ColumnValue ='AB' 
    where A1=1 AND A2 =1 AND a3 =1 AND a4 =1 AND b1 =1 AND b2 =1 AND b3 =1 AND b4=1
    END

   ELSE IF (Select Count(*) from table where A1 =1 and A3 =1 )>0

    BEGIN
     Update MyTable set columnValue ='A'
     where A1 =1 and A3 =1
    END