Case within Case when combining multiple columns into one - sql

Question

I'm trying to create a query that will take multiple columns in a View and bring it into one column in the query. The values from each column needs to be separated by '|' (pipe).
I've tried:
1) (expression1 + '|' + expression2) AS xxxx, but if one expression has a null value, it makes the results 'null'.
2) CAST (expression1 as varchar (10)) + '|' + CAST (expression2 as varchar (10)) AS xxxx, but get the same results.
3) CASE (expression1 is null) then (' ') else (expression1) +'|' + CASE (expression2 is null) then (' ') else (expression2) END AS xxxx, but I get a syntax error near the keyword 'AS'.
Here's the full query using CASE.
SELECT DISTINCT dbo.REG.BUILDING, dbo.REG.CURRENT_STATUS, dbo.REG_CONTACT.LOGIN_ID, dbo.REG.LAST_NAME
, CASE WHEN dbo.View_MYAccess_Period1.CRSGRP1 is null then ' ' else dbo.View_MYAccess_Period1.CRSGRP1 + ' |' +
CASE WHEN dbo.View_MYAccess_Period2.CRSGRP2 is null then ' ' else dbo.View_MYAccess_Period2.CRSGRP2
END AS CRSGRP
FROM dbo.REG_CONTACT RIGHT OUTER JOIN
dbo.REG_STU_CONTACT ON dbo.REG_CONTACT.CONTACT_ID = dbo.REG_STU_CONTACT.CONTACT_ID RIGHT OUTER JOIN
dbo.REG ON dbo.REG_STU_CONTACT.STUDENT_ID = dbo.REG.STUDENT_ID LEFT OUTER JOIN
dbo.View_MYAccess_Period1 ON dbo.REG.STUDENT_ID = dbo.View_MYAccess_Period1.STUDENT_ID LEFT OUTER JOIN
dbo.View_MYAccess_Period2 ON dbo.REG.STUDENT_ID = dbo.View_MYAccess_Period2.STUDENT_ID
Any help for this newbie would be greatly appreciated!

Answer 1

Use ISNULL function,
SELECT DISTINCT dbo.REG.BUILDING, dbo.REG.CURRENT_STATUS, dbo.REG_CONTACT.LOGIN_ID, dbo.REG.LAST_NAME
, ISNULL(dbo.View_MYAccess_Period1.CRSGRP1,' ') + ' |' +
ISNULL(dbo.View_MYAccess_Period2.CRSGRP2,' ') CRSGRP
FROM dbo.REG_CONTACT RIGHT OUTER JOIN
dbo.REG_STU_CONTACT ON dbo.REG_CONTACT.CONTACT_ID = dbo.REG_STU_CONTACT.CONTACT_ID RIGHT OUTER JOIN
dbo.REG ON dbo.REG_STU_CONTACT.STUDENT_ID = dbo.REG.STUDENT_ID LEFT OUTER JOIN
dbo.View_MYAccess_Period1 ON dbo.REG.STUDENT_ID = dbo.View_MYAccess_Period1.STUDENT_ID LEFT OUTER JOIN
dbo.View_MYAccess_Period2 ON dbo.REG.STUDENT_ID = dbo.View_MYAccess_Period2.STUDENT_ID

Answer 2

In example 1, you might use the COALESCE(expression, fallback) function to force expression to return a fallback value if the expression is null. (Then tweak the rest of the logic accordingly.)
In your example 3, you need another END keyword:
CASE
(expression1 is null) then (' ')
ELSE (expression1) +'|' +
CASE (expression2 is null) then (' ') else (expression2) END
END AS xxxx