如何使用SQL中的另一个表数据更新表的多列？

Question

I have two tables A , B

A

Id  Col1  Col2 Col3
100  Null Null  0

B

Id   Colx   Colz Coly
100  1234    10   4           
100  2345    12   4 

Expected Result:

Id  Col1  Col2 Col3
100  1234 2345  4

I am trying to get the Colx of table B into Col1 , Col2 respectively based on Colz however not getting the expected results. below is my query -

 UPDATE    a
  SET       a.Col1 = CASE WHEN b.Colz=10 THEN b.Colx END,
            a.Col2 = CASE WHEN b.Colz=12 THEN b.Colx END,
            a.Col3=b.Coly
  FROM      A a
            JOIN B b  ON b.Id = a.Id

Please help

Answer 1

You can join the same table twice with different conditions like this:

UPDATE    a
  SET       a.Col1 = b1.Colx 
            a.Col2 = b2.Colx,
            a.Col3=b1.Coly
  FROM      A a
  JOIN B b1  ON b1.Id = a.Id AND b1.Colz=10 
  JOIN B b2  ON b2.Id = a.Id AND b2.Colz=12