How do I remove a trailing comma when an alias is involved? - sql

Question

CASE WHEN Col1 = 1 THEN
(CASE WHEN Col2=2 THEN 'a' + ', ' END) +
(CASE WHEN Col3=2 THEN 'b' + ', ' END) +
(CASE WHEN Col4=2 THEN 'c' END)
END as Names
Names can be a,b,c or a,b, or b,
How do I remove the character "," at the end? I cannot use replace or stuff etc functions as "Names" is an alias
original Query:
CASE WHEN ht.bTax=0 then
ISNULL(CASE WHEN (r1.iOccType=2) THEN p1.SFIRSTNAME + ' ' + p1.ULASTNAME END,'') +
ISNULL(CASE WHEN (r2.iOcctType=2) THEN p2.SFIRSTNAME + ' ' + p2.ULASTNAME + ', ' END, '') +
ISNULL(CASE WHEN (r3.iOccType=2) THEN p3.SFIRSTNAME + ' ' + p3.ULASTNAME + ', ' END, '') +
ISNULL(CASE WHEN (r4.iOccType=2) THEN p4.SFIRSTNAME + ' ' + p4.ULASTNAME + ', ' END, '') +
ISNULL(CASE WHEN (r5.iOccType=2) THEN p5.SFIRSTNAME + ' ' + p5.ULASTNAME + ', ' END, '')
End AS Names

Answer 1

My solution would be to add the comma to the end of the 'c' result exactly the same as the others then remove the last two characters from the string after the fact. I think it would be cleaner to put your first statement into a cte then select from it while cleaning up the string then:
with cte as(
Select
CASE WHEN 1 = 1 THEN
(CASE WHEN Col2=2 THEN 'a, ' ELSE '' END) +
(CASE WHEN Col3=2 THEN 'b, ' ELSE '' END) +
(CASE WHEN Col3=2 THEN 'c, ' ELSE '' END)
END as Names
)
select SUBSTRING(Names, 0, Len(Names)) as Names from CTE
Alternatively you can just do it inline but you'll have to repeat your string construction a second time this way.
CASE WHEN Col1 = 1 THEN
SUBSTRING(
(CASE WHEN Col2=2 THEN 'a, ' ELSE '' END) +
(CASE WHEN Col3=2 THEN 'b, ' ELSE '' END) +
(CASE WHEN Col4=2 THEN 'c, ' ELSE '' END)
,0, LEN(
(CASE WHEN Col2=2 THEN 'a, ' ELSE '' END) +
(CASE WHEN Col3=2 THEN 'b, ' ELSE '' END) +
(CASE WHEN Col4=2 THEN 'c, ' ELSE '' END)
))
END as Names
Just to explain what I'm doing here:
SUBSTRING (string, start point, end point) - returns contents of string from start point (0 is beginning) and the end point
LEN (string) - returns the amount of characters in the string
By passing 0 as the start and the LEN() of the string as the last parameter, it will return the full string missing the last character (because the index starts at zero). Usually you would have to put LEN() - 1 but apparently LEN does not count the last empty character.