NEED HELP STRUCTURING A SUBSELECT - INVALIS IDENTIFIER ERROR

Question

This is my 1st post to this PL/SQL forum. I've used TSQL up to now; first job with PL/SQL and Oracle DB. I'm getting a "INVALID IDENTIFIER" error on the ORDER BY line (next to last line in code) in the following code. I haven't doen a lot of subselects and none with grouping. All I'm trying to do is get a count of states my customers are in... Any ideas what might be causing the problem, or a better way to structure this? (I tried the subselect in the SELECT statement as well with no luck there either)
-- count and list All states by state zipcode resolution
SELECT st.state, COUNT(*) AS count_by_state
FROM ADM.USR u
INNER JOIN
SELECT
CASE
WHEN zipcode BETWEEN 99501 AND 99950 THEN 'AK' -- Alaska
WHEN zipcode BETWEEN 35004 AND 36925 THEN 'AL' -- Alabama
WHEN zipcode BETWEEN 71601 AND 72959 THEN 'AR' -- Arkansas
WHEN zipcode BETWEEN 75502 AND 75502 THEN 'AR' -- Arkansas( Texarkana)
WHEN zipcode BETWEEN 85001 AND 86556 THEN 'AZ' -- Arizona
WHEN zipcode BETWEEN 82001 AND 83128 THEN 'WY' -- Wyoming
ELSE NULL
END AS state
FROM CUST.USR_PRFL
ORDER BY state) st ON u.usr_id = st.usr_id
GROUP BY st.state;
Edited by: 927929 on Apr 16, 2012 7:05 AM
Edited by: 927929 on Apr 16, 2012 7:07 AM

Answer 1

try
SELECT st.state, COUNT(*) AS count_by_state
FROM ADM.USR u
INNER JOIN CUST.USR_PRFL up ON u.usr_id = up.usr_id
INNER JOIN
SELECT
CASE
WHEN zipcode BETWEEN 99501 AND 99950 THEN 'AK' -- Alaska
WHEN zipcode BETWEEN 35004 AND 36925 THEN 'AL' -- Alabama
WHEN zipcode BETWEEN 71601 AND 72959 THEN 'AR' -- Arkansas
WHEN zipcode BETWEEN 75502 AND 75502 THEN 'AR' -- Arkansas( Texarkana)
WHEN zipcode BETWEEN 85001 AND 86556 THEN 'AZ' -- Arizona
WHEN zipcode BETWEEN 82001 AND 83128 THEN 'WY' -- Wyoming
ELSE NULL
END AS state
FROM CUST.USR_PRFL
--ORDER BY state
) st
-- any relation beetwen? like "ON u.usr_id = up.usr_id" above
GROUP BY st.state
ORDER BY state;