Question

Wrong results for UNION ALL

Asked by: lirwan

Our developer construct the SQL statement (refer to ALL_SQL.sql) using UNION ALL and it returns inconsistent data on certain policy.

When I split the source code into 2, it returns consistent data (SQL1.sql, SQL2.sql).

Is there a bug in ORACLE? our oracle dba advice us not to use UNION ALL. Is it true that UNION ALL shouldn't be used and it causes problem? If yes, what kind of problem?

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Asked On
2009-11-06 at 01:20:02ID24877357
Tags

Oracle 10.2.0.2

Topic

Oracle 10.x

Participating Experts
2
Points
500
Comments
11

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Answers

 

by: joaoalmeidaPosted on 2009-11-06 at 01:32:33ID: 25757764

Try to have the columns in the same position with the same name.

For instance you have

                s.create_time in first select
                s.update_time in second select

and CreateTime in the second part of the query.

Regards,

Joao

 

by: rrjegan17Posted on 2009-11-06 at 01:32:55ID: 25757768

Have checked your code now..
You have used DISTINCT in all individual SELECT statement and UNION / UNION ALL interchangeably.

Since you haven't provided the results, I would request you to

1. Remove DISTINCT in all individual statements
2. Replace UNION ALL with UNION

And try it out once.

 

by: lirwanPosted on 2009-11-06 at 05:15:26ID: 25758774

Here are the result..... after I execute the SQL query (ALL_SQL.sql)

Please refer to the PREMIUM column

 

by: lirwanPosted on 2009-11-06 at 06:20:09ID: 25759285

Hi Guys,

I believe I need to revise the title from "Wrong results for UNION ALL" to "Different result for same QUERY using UNION ALL".

Please help.......

 

 

by: rrjegan17Posted on 2009-11-06 at 07:05:37ID: 25759674

Checked your Result sets attached..
And bit strange..

Have you tried removing DISTINCT keyword at all SELECT statements
& Replacing UNION ALL with UNION in all your queries and give it a try..

 

by: joaoalmeidaPosted on 2009-11-06 at 07:07:12ID: 25759699


The two rows that have problems are from Query1 or from Query2?

 

by: lirwanPosted on 2009-11-07 at 05:29:01ID: 25766239

ALL_SQL.sql = SQL1.sql + SQL2.sql

The 2 rows comes from SQL2.sql, however the funny thing is when I execute only SQL2.sql, that 2 rows returns consistent data.

I'm strongly believe that it's oracle bug, can somebody explain to me why? Is there any limitation with the no of UNION ALL that we can use? Is it because SQL1.sql don't have GROUP BY but SQL2.sql have GROUP BY?

 

by: rrjegan17Posted on 2009-11-07 at 18:09:12ID: 25769099

lirwan,
     Have you tried out my suggestions..

 

by: lirwanPosted on 2009-11-11 at 21:38:17ID: 25801780

Apologies for late reply.

Our developers tried the following and it returns consistent value:

SQL2 UNION ALL SQL1

However the question on why SQL1 UNION ALL SQL2 returns inconsitent value is still remained.

 

by: rrjegan17Posted on 2009-11-11 at 21:44:06ID: 25801793

>> However the question on why SQL1 UNION ALL SQL2 returns inconsitent value is still remained.

UNION ALL would just concatenate all records in both SQL1 and SQL2.
UNION would concatenate all records from both SQL1 and SQL2 and would select only the DISTINCT records..

Now try using UNION statement to get unique results if you have duplicate records by any chance..

 

by: lirwanPosted on 2009-11-23 at 00:34:25ID: 31650946

The solution provided resolve the inconsistency problem, however it still does not provide the answer why SQL2 UNION ALL SQL1 is having consistent result.

20120131-EE-VQP-002

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