T-SQL replace NULL values in result I'm at loss with this. What would be the simples way to achieve this?

I have "Customers" table like this:

USER_ID| NAME    | J_ID   |K_ID    |Y_ID
-----------------------------------------
    1  |  CUST1  |  A     |  1     |  AB
    2  |  CUST2  |  B     |  2     |  NULL
    3  |  CUST3  |  C     |  3     |  EF
    4  |  CUST4  |  NULL  |  NULL  |  GH
    5  |  CUST5  |  E     |  5     |  IJ


Then "R_ID" table like this:

   R_ID  | Y_ID    
------------------
    1A9  |  AB  
    2B8  |  CD  
    3C7  |  EF  
    4D6  |  GH  
    5E5  |  IJ  


Then "JK_ID" table like this:

   R_ID  | J_ID | K_ID
-----------------------
    1A9  |  A  |  1
    2B8  |  B  |  2
    3C7  |  C  |  3
    4D6  |  D  |  4
    5E5  |  E  |  5


This is what I would like to get:

USER_ID| NAME    | J_ID   |K_ID    |Y_ID
-----------------------------------------
    1  |  CUST1  |  A     |  1     |  AB
    2  |  CUST2  |  B     |  2     |  CD
    3  |  CUST3  |  C     |  3     |  EF
    4  |  CUST4  |  D     |  4     |  GH
    5  |  CUST5  |  E     |  5     |  IJ


So I need to get the missing values from R_ID or JK_ID tables by joining those. But what is the simplest way to get that result, so that the nulls are replaced by the values from joined tables?
One way to accomplish this is to use LEFT OUTER JOIN along with COALESCE. To get the missing values in the J_ID and K_ID column you can join to R_ID and JK_ID. To get the missing values in the Y_ID column you can join to JK_ID and R_ID.

Something close to the following should work:

SELECT
  cus.USER_ID
, cus.NAME
, COALESCE(cus.J_ID, r_to_jk.J_ID) AS J_ID
, COALESCE(cus.K_ID, r_to_jk.K_ID) AS K_ID
, COALESCE(cus.Y_ID, r_to_y.Y_ID) AS J_ID
FROM Customers cus
LEFT OUTER JOIN R_ID y_to_r ON cus.Y_ID = y_to_r.Y_ID
LEFT OUTER JOIN JK_ID r_to_jk ON y_to_r.R_ID = r_to_jk.R_ID
LEFT OUTER JOIN JK_ID jk_to_r ON cus.J_ID = jk_to_r.J_ID AND cus.K_ID = jk_to_r.K_ID
LEFT OUTER JOIN R_ID r_to_y ON jk_to_r.R_ID = r_to_y.R_ID;