t=table(1..500000 as id, take(['600000.SH','600001.SH','600002.SH','000002.SZ','000001.SZ'],500000)  as x);

可以通过以下三种方法修改：

update t set x = iif(right(x,3)=='.SH', take("1",size(x))+left(x,6),take("0",size(x))+left(x,6)) 
update t set x = iif(right(x,3)=='.SH',"1"+string(left(x,6)),"6"+string(left(x,6)))
update t set x = iif(right(x,3)=='.SH',"1".add(left(x,6)),"6".add(left(x,6)))