Using order by in Union ALL

Question

hi Following is my query and am unable to accomplish my order by statement in Union All . please help me in this.
<code>
SELECT b.audit_trail_id,
TO_CHAR (b.last_update_date, 'DD-Mon-YYYY') "Revision Date",
(u.last_name || ', ' || u.first_name || ' ' || u.mi) "By",
b.col_name "Field",
b.new_value "New Value",b.previous_value "Old Value",
a.lot_id,
b.comment_text "Comments"
FROM clem_audit_trail b,lot a, users u
WHERE a.lot_id = b.lot_id(+)
AND u.user_id(+) = b.last_update_user_id
AND a.lot_id in (select lot_id from request_lot where request_id = 51914)
AND col_name IN
('Interim Release Date',
'Final Disposition Date',
'On Time Disposition',
'Intended Use',
'REJECTS_YN',
'# of QARs',
'# of Quality Events',
'# of LIRs',
'# of Change Controls',
'# of Batch Records',
'# of GMP Batch Records',
'EXPLANATION',
'QA Notes',
'GDMS_LINK')
AND UPPER (table_name) IN('LOT') order by b.last_update_date
UNION ALL
SELECT b.audit_trail_id,
TO_CHAR (b.last_update_date, 'DD-Mon-YYYY') "Revision Date",
(u.last_name || ', ' || u.first_name || ' ' || u.mi) "By",
b.col_name "Field",
b.new_value "New Value",b.previous_value "Old Value",
r.request_id,
b.comment_text "Comments"
FROM clem b,request r, users u
WHERE r.request_id = b.request_id(+)
AND u.user_id(+) = b.last_update_user_id
AND r.request_id = 51914
AND UPPER (table_name) IN ('REQUEST') AND
b.col_name IN ('Partial Release',
'All QP Docs in GDMS',
'Number of Batch Records',
'Request',
'QP Issues',
'Snag Comments',
'Responsible Group',
'Reason Late',
'Study Impact',
'Other Details',
'Request Status',
'QP Link to GDMS'
) order by b.last_update_date
</code>
If i execute individually it works fine, if i use union all it throughs error for me.
Any suggestion...

Answer 1

Hi,
In a set operation (such as UNION) table aliases (such as b.) only have meaning within the branch in which they are defined. The ORDER BY clause is not part of any 1 branch, so a table alias can't be used there.
In most cases, you can use a column name (or alias) from the first branch, like this:
SELECT    b.audit_trail_id,
          TO_CHAR (b.last_update_date, 'DD-Mon-YYYY') "Revision Date",
order by  "Revision Date"
;and you can always order by column number, like this:
SELECT    b.audit_trail_id,
          TO_CHAR (b.last_update_date, 'DD-Mon-YYYY') "Revision Date",
order by  2
;In this case, however, there's an extra problem. You're transforming the DATE to a string in the SELECT clause. The string is all that's available in the ORDER BY clause, and the string '19-NOV-2012' comes after the string '01-JAN-2015', because the character '1' comes after '0'. Perhaps the simplest solution is to have your front end, and not the query, format the dates. In SQL*Plus, you can do this:
ALTER SESSION  SET NLS_DATE_FORMAT = 'DD-MON-YYYY';
SELECT    b.audit_trail_id,
          b.last_update_date    AS "Revision Date",
order by  2
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all the tables involved, and the results you want from that data.
Explain, using specific examples, how you get those results from that data.
Always say what version of Oracle you're using (e.g. 11.2.0.2.0).
See the forum FAQ {message:id=9360002}