nested sorting using nested case statement

[Radhakant Samal]

i am trying to sort using case statement but in branching ie

suppose i hava a table which has state and district as two columns.
so when i am retrieving data first it should sort the state wise then
district name with respect to the state name.

order by state case
when state_1 then 1
when state_2 then 2
when state_3 then 3
else state
end;
what is my requirement is when it displays the state_1 then it should
display all the district related to state_1 in a sorted manner.

so if i am using nested case it displays error. i am using like below

order by state case
when state_1 then order by district case
when dis_1 then 1
when dis_2 then 2
.
.
.
end
when state_2 then order by district
.
.
when state_2 then order by district
.
.
end,
but it is not working, kindly let me know the correct way to get this.