Trim extra white space within column - sql

Question

I have the following select that is converting a name from Lastname, Firstname format into Firstname Lastname format. It seems to be adding extra white space between the first name and the last name
SELECT substring(D.NAME, charindex(',', replace(D.NAME, ' ', '')) + 1, len(D.NAME))
+ ' '
+ left(D.NAME, charindex(',', D.NAME) -1) AS First_Last
FROM TEST_TABLE D
Here are a few examples of the output I'm getting now:
Johnnyyy Smithsonnn
Kimmey Test1
Denise Stuffing
Desired Format (single space between first and last name):
Johnnyyy Smithsonnn
Kimmey Test1
Denise Stuffing

Answer 1

I tend to like this technique. In this example we use a rare replacement pattern of †‡, but you can use <> and ><
Note: The outer ltrim(rtrim( ... )) is optional, I keep it as a "just in case".
Example
Select NewValue = ltrim(rtrim(replace(replace(replace([Name],' ','†‡'),'‡†',''),'†‡',' ')))
From YourTable
Returns
NewValue
Johnnyyy Smithsonnn
Kimmey Test1
Denise Stuffing

Answer 2

Maybe there are names with or without , or with or without spaces after the ,, or other inconsistencies.
Anyway you can use ltrim(rtrim()) before concatenating:
select
case
when d.name like '%,%' then
ltrim(rtrim(substring(d.name, charindex(',', name) + 1, len(d.name))))
+ ' ' +
ltrim(rtrim(left(D.NAME, charindex(',', d.name) -1)))
when d.name like '% %' then
ltrim(rtrim(substring(d.name, charindex(' ', name) + 1, len(d.name))))
+ ' ' +
ltrim(rtrim(left(D.NAME, charindex(' ', d.name) -1)))
else ltrim(rtrim(d.name))
end AS First_Last

Answer 3

Try:
select ltrim(rtrim(left(D.NAME, charindex(',', D.NAME, 0) - 1)))
+ ' '
+ ltrim(rtrim(right(D.NAME, len(D.NAME) - charindex(',', D.NAME, 0))))
from TEST_TABLE D
This worked on some test data I used below:
insert into #Test ([Name]) values ('Johnnyyy, Smithsonnn')
insert into #Test ([Name]) values ('Kimmey, Test1')
insert into #Test ([Name]) values ('Denise, Stuffing')
Which gives the intended result:
Johnnyyy Smithsonnn
Kimmey Test1
Denise Stuffing

Answer 4

I think you intend to do the replace of spaces after extracting the name. So:
SELECT (replace(left(D.NAME, charindex(',', D.NAME + ',') + 1), ' ', '') +
' ' +
left(D.NAME, charindex(',', D.NAME + ',') - 1)
) AS First_Last
FROM TEST_TABLE D;
This also adds a comma for the charindex() so the comma is optional.