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NULL is returned as zero through a left join in simple VIEW [CORE514] #867

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firebird-issue-importer opened this issue Jan 9, 2001 · 5 comments

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@firebird-issue-importer firebird-issue-importer commented Jan 9, 2001

Submitted by: Claudio Valderrama C. (robocop)

Assigned to: Claudio Valderrama C. (robocop)

Is duplicated by CORE871

SFID: 228135#⁠
Submitted By: robocop

-----Original Message-----
From: Ondrej Kelle
Sent: Domingo 7 de Enero de 2001 6:19
To: Claudio Valderrama
Subject: RE: [IBO] NULL incorrectly returned as 0 through a left outer join view

Hello Claudio,

Thanks for your response! I'm attaching the SQL scripts. Please create an empty test database. You can then connect to the database using isql and issue the following command:

input 'create all.sql';

This should create the domains, tables, views etc. and insert some test data. With the test data please try the following:

select pvb.project, pvb.mjr, pvb.mnr, pvb.rls, pvb.bld, http://b.id, b.priority,
b.entered_by, b.closed, b.status
from bug b left outer join
project_version_bug pvb
on (pvb.bug = http://b.id) where b.assigned_to = user;

 PROJECT     MJR     MNR     RLS     BLD           ID PRIORITY

ENTERED_BY CLOSED STATUS
============ ======= ======= ======= ======= ============ ========
=============================== ====== ======

       1       0       0       0       0            1        1 SYSDBA

N A
1 0 1 0 0 1 1 SYSDBA
N A
<null> <null> <null> <null> <null> 2 1 SYSDBA
N A

This is correct, you can see the null values where there are no records in project_version_bug for bug id 2.

However, using the BUG_ASSIGNED view (which is defined with exactly the same SQL statement) I get the following:

select * from bug_assigned;

 PROJECT     MJR     MNR     RLS     BLD           ID PRIORITY

ENTERED_BY CLOSED STATUS
============ ======= ======= ======= ======= ============ ========
=============================== ====== ======

       1       0       0       0       0            1        1 SYSDBA

N A
1 0 1 0 0 1 1 SYSDBA
N A
0 0 0 0 0 2 1 SYSDBA
N A

or even this:

select * from bug_assigned where project is null;

 PROJECT     MJR     MNR     RLS     BLD           ID PRIORITY

ENTERED_BY CLOSED STATUS
============ ======= ======= ======= ======= ============ ========
=============================== ====== ======

       0       0       0       0       0            2        1 SYSDBA

N A

Here all the null values as a result of the left outer join are presented as
zeros.

Thanks a lot for your interest in this problem!
TOndrej
-----Original Message-----

This is a case using one column to demonstrate even clearer the bug:
select project
from bug_assigned
where project is null;
=> produces a zero as the result. The engine seems to recognize that the value is NULL so it honors the WHERE clause, but it returns zero. The view is very simple to be considered a boundary case.

The scripts to create both data and metadata (see instructions at the top of the email I copied above) are available at
http://www.cvalde.com/bugs/test_view.zip

C.

====== Test Details ======

See test for core-871

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@firebird-issue-importer firebird-issue-importer commented Jun 14, 2006

Commented by: Alice F. Bird (firebirds)

Date: 2002-02-26 08:46
Sender: robocop
Logged In: YES
user_id=62823

This is a trivial example:
/* SF Bug #⁠228135 */
create table t(a int);
insert into t values(1);
create domain dom_u int not null;
create table u(b dom_u);
create view v as select t.a, u.b from t left join u on t.a
= u.b;
commit;
select * from v;

/*
A B
============ ============

       1            0

*/

Table U has no records, column B should be NULL instead!

create view v2(a, c) as select t.a, u.b+0 from t left join
u on t.a = u.b;
commit;
select * from v2;

/*
A C
============ =====================

       1                &lt;null&gt;

*/

By forcing an aggregate, we have done the trick. Now, the
trick is no longer necessary.

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@firebird-issue-importer firebird-issue-importer commented Jul 27, 2006

Modified by: @dyemanov

Link: This issue is duplicated by CORE871 [ CORE871 ]

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@firebird-issue-importer firebird-issue-importer commented Jan 28, 2008

Modified by: @pcisar

Workflow: jira [ 10538 ] => Firebird [ 14852 ]

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@firebird-issue-importer firebird-issue-importer commented Jan 19, 2016

Modified by: @pavel-zotov

QA Status: No test

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@firebird-issue-importer firebird-issue-importer commented Sep 12, 2016

Modified by: @pavel-zotov

status: Closed [ 6 ] => Closed [ 6 ]

QA Status: No test => Covered by another test(s)

Test Details: See test for core-871

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