Alternatively, if you really need to use Replace instead of Stuff for this, try using Substring to get the piece that you want to replace. Build the Substring parameters the same way I did the Stuff position and length. Then use that as the first argument for the Replace function.

SELECT string,

SUBSTRING(string, CHARINDEX('%', string, 1),

CHARINDEX('%', string, CHARINDEX('%', string, 1) + 1) - CHARINDEX('%', string, 1) + 1),

REPLACE(string,

SUBSTRING(string, CHARINDEX('%', string, 1),

CHARINDEX('%', string, CHARINDEX('%', string, 1) + 1) - CHARINDEX('%', string, 1) + 1),

'replaced')

FROM (SELECT 'somestring+%sometext%' AS string

UNION ALL

SELECT '%sometext%'

UNION ALL

SELECT 'somestring+%sometext%+somesecondstring') AS Example;

Either will work. Just thought of the nested Replace(Substring()) version second is all.