You can use CASE w/i a GROUP BY.

You can also use CASE w/i a SUM to control which values get aggregated. For example:

SELECT

a, b,

SUM(CASE WHEN KTVID = '12345' AND KTVValueType = '02.KTVSCHAF' THEN Value ELSE 0 END) AS KTVID_12345_02_Total,

SUM(Value) AS All_Values_Total

FROM

dbo.tablename

GROUP BY

a, b