>>>I used RTRIM(FORMAT(1234567.89, 'N', 'en-US')) to format a number with thousand separators and decimals. However this works only since SQL Server 2012 and above.
>>>
>>>So 1234567.89 should be "1,234,567.89" or 10.00 should be "10.00"
>>>
>>>Best alternative I found is LTRIM(STR(1234567.89,14,2)), but this of course does not produce thousands separators.
>>>
>>>I tried RTRIM(REPLACE(CONVERT(VARCHAR,CONVERT(MONEY,1234567.89),1), '.00','')), but this would cut off decimals if they are #.00.
>>>
>>>Is there another way to have the best of both worlds?
>>
>>Why you didn't do this in your frontend?
>
>There are two reasons:
>1) The sql query is built in a central code snippet that is being used in different places. I like to have the output formatted already in the result, so that all places that are using this query don't need to be changed.
>2) The text is part of a larger text that would need to be processed in a post routing, but the result is very large and would slow down the process.

You can write your own function like Rick suggested (but in TSQL :-) ) but that can slow down the query.
Of course you can check the version of SQL Server to know if you should use that function or no.