replace,substring

Question

select popedom1,replace(popedom1,substring(popedom1,18,2),11) from v_alluser
where office='hlsdl' and substring(popedom1,18,2)<>'11' 
and substring(popedom1,22,1)='1' and substring(popedom1,25,1)='1' 
and useid='SUNDYDENGDL' and void_flag=02列的结果分别为:
00010000000000101000010011100001000000110000000000
11011111111111101111111111111111111111111111111111我想要的结果是这样的,只要求在
00010000000000101000010011100001000000110000000000
中把里面的18和19为替换为11即可.如下结果
00010000000000101110010011100001000000110000000000
但是我用以上语句替换却是这一下结果
11011111111111101111111111111111111111111111111111

Answer 1

select stuff('00010000000000101000010011100001000000110000000000',18,2,'11')

Answer 2

select popedom1,STUFF(popedom1,18,2,'11'') from v_alluser

Answer 3

select popedom1,left(popedom1,17)+'11'+right(popedom1,len(popedom1)-19)