ID B C
1 2 9 ( C is sum of column B 2+4+3) row 1+2+3
2 4 8 (C is sum of column B 4+3+1) row 2+3+4
3 3 5 (C is sum of column B 3+1+1) row 3+4+5
4 1 6 (C is sum of column B 1+1+4) row 4+5+6
5 1 5 (C is sum of column B 1+4+0) row 5+6+0
6 4 4
how do I get column C by sum of 3 rows in column B
using SQL server 2008R2