Best way to put commas into large numbers
TSQL's FORMAT function can do that. EG
select format(1232131312342132123.2222,'0,###.##')
outputs
1,232,131,312,342,132,123.22
If you want to use a different separator, you still use ,
which has a special meaning in .Net format string, and then replace the ,
with something else. EG:
select replace(format(123445678.2222,'#,###.##'),',','_')
outputs
123_445_678.22
If you're on SQL Server 2012+, and you want to do it (without decimal places):
SELECT FORMAT(2036150, N'N0')
If you're on an earlier version, you have to jump through some hoops:
SELECT REPLACE(CONVERT(NVARCHAR(30), CAST((2036150) AS MONEY), 1), N'.00', N'')