Bug #618 UNION clause does not work properly.
Submitted: 6 Jun 2003 22:46 Modified: 3 Jul 2003 5:51
Reporter: Asish Kumar Samanta Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server Severity:S2 (Serious)
Version:4.0.12 OS:Microsoft Windows (Windows NT)
Assigned to: CPU Architecture:Any

[6 Jun 2003 22:46] Asish Kumar Samanta
Description:
When I run the sql query :

select a.group_id as "Select", a.group_name as "Group Name", 
date_format(a.group_created_date,"%M %e, %Y %H:%i") as "Created Date",
date_format(a.last_modification_date,"%M %e, %Y %H:%i") as "Last Modified", a.learning_style as "Style" , 
count(c.group_id) as "No. of Members" from student_group a left join 
student_group_association c on a.group_id = c.group_id 
where a.group_id = 'FIN' group by c.group_id, a.group_name, a.group_id union
select a.group_id as "Select", a.group_name as "Group Name", 
date_format(a.group_created_date,"%M %e, %Y %H:%i") as "Created Date",
date_format(a.last_modification_date,"%M %e, %Y %H:%i") as "Last Modified", a.learning_style as "Style" , 
count(c.group_id) as "No. of Members" from student_group a left join student_group_association c 
on a.group_id = c.group_id 
where a.group_id <> 'FIN' group by c.group_id, a.group_name, a.group_id;

the buggy result will come:

+--------+-------------+--------------------+--------------------+----------+----------------+
| Select | Group Name  | Created Date       | Last Modified      | Style    | No. of Members |
+--------+-------------+--------------------+--------------------+----------+----------------+
| FIN    | Finance     | June 6, 2003 19:32 | June 6, 2003 19:32 | Advanced |              1 |
| DEV    | Development | June 6, 2003 19:38 | June 6, 2003 19:38 | Expert   |              0 |
+--------+-------------+--------------------+--------------------+----------+----------------+
2 rows in set (0.00 sec). Actually in the count column will be 0 but in  first row it shows 1.

If I ommit the "Union" clause, it shows the result properly:

select a.group_id as "Select", a.group_name as "Group Name", 
date_format(a.group_created_date,"%M %e, %Y %H:%i") as "Created Date",
date_format(a.last_modification_date,"%M %e, %Y %H:%i") as "Last Modified", a.learning_style as "Style" , 
count(c.group_id) as "No. of Members" from student_group a left join 
student_group_association c on a.group_id = c.group_id 
where a.group_id = 'FIN' group by c.group_id, a.group_name, a.group_id;

+--------+------------+--------------------+--------------------+----------+----------------+
| Select | Group Name | Created Date       | Last Modified      | Style    | No. of Members |
+--------+------------+--------------------+--------------------+----------+----------------+
| FIN    | Finance    | June 6, 2003 19:32 | June 6, 2003 19:32 | Advanced |              0 |
+--------+------------+--------------------+--------------------+----------+----------------+
1 row in set (0.00 sec)

and
 
+--------+-------------+--------------------+--------------------+--------+----------------+
| Select | Group Name  | Created Date       | Last Modified      | Style  | No. of Members |
+--------+-------------+--------------------+--------------------+--------+----------------+
| DEV    | Development | June 6, 2003 19:38 | June 6, 2003 19:38 | Expert |              0 |
+--------+-------------+--------------------+--------------------+--------+----------------+
1 row in set (0.00 sec)

How to repeat:
When I run the sql query :

select a.group_id as "Select", a.group_name as "Group Name", 
date_format(a.group_created_date,"%M %e, %Y %H:%i") as "Created Date",
date_format(a.last_modification_date,"%M %e, %Y %H:%i") as "Last Modified", a.learning_style as "Style" , 
count(c.group_id) as "No. of Members" from student_group a left join 
student_group_association c on a.group_id = c.group_id 
where a.group_id = 'FIN' group by c.group_id, a.group_name, a.group_id union
select a.group_id as "Select", a.group_name as "Group Name", 
date_format(a.group_created_date,"%M %e, %Y %H:%i") as "Created Date",
date_format(a.last_modification_date,"%M %e, %Y %H:%i") as "Last Modified", a.learning_style as "Style" , 
count(c.group_id) as "No. of Members" from student_group a left join student_group_association c 
on a.group_id = c.group_id 
where a.group_id <> 'FIN' group by c.group_id, a.group_name, a.group_id;

the buggy result will come:

+--------+-------------+--------------------+--------------------+----------+----------------+
| Select | Group Name  | Created Date       | Last Modified      | Style    | No. of Members |
+--------+-------------+--------------------+--------------------+----------+----------------+
| FIN    | Finance     | June 6, 2003 19:32 | June 6, 2003 19:32 | Advanced |              1 |
| DEV    | Development | June 6, 2003 19:38 | June 6, 2003 19:38 | Expert   |              0 |
+--------+-------------+--------------------+--------------------+----------+----------------+
2 rows in set (0.00 sec). Actually in the count column will be 0 but in  first row it shows 1.

If I ommit the "Union" clause, it shows the result properly:

select a.group_id as "Select", a.group_name as "Group Name", 
date_format(a.group_created_date,"%M %e, %Y %H:%i") as "Created Date",
date_format(a.last_modification_date,"%M %e, %Y %H:%i") as "Last Modified", a.learning_style as "Style" , 
count(c.group_id) as "No. of Members" from student_group a left join 
student_group_association c on a.group_id = c.group_id 
where a.group_id = 'FIN' group by c.group_id, a.group_name, a.group_id;

+--------+------------+--------------------+--------------------+----------+----------------+
| Select | Group Name | Created Date       | Last Modified      | Style    | No. of Members |
+--------+------------+--------------------+--------------------+----------+----------------+
| FIN    | Finance    | June 6, 2003 19:32 | June 6, 2003 19:32 | Advanced |              0 |
+--------+------------+--------------------+--------------------+----------+----------------+
1 row in set (0.00 sec)

and
 
+--------+-------------+--------------------+--------------------+--------+----------------+
| Select | Group Name  | Created Date       | Last Modified      | Style  | No. of Members |
+--------+-------------+--------------------+--------------------+--------+----------------+
| DEV    | Development | June 6, 2003 19:38 | June 6, 2003 19:38 | Expert |              0 |
+--------+-------------+--------------------+--------------------+--------+----------------+
1 row in set (0.00 sec)

Suggested fix:
I think, there is a problem in Union clause. I also run the above sql query in SQL Server and Oracle, it works properly.
[7 Jun 2003 3:23] Sinisa Milivojevic
We are very interested in fixing this bug.

In order to be able to do that, we need tables involved.

Upload them to :

ftp://support.mysql.com:/pub/mysql/secret

and let us know a name of the file.
[8 Jun 2003 22:35] Asish Kumar Samanta
Hi, 

I am unable to upload the file. I paste it here. Pls copy it. Run this query, it creates two tables with the name "student_group" and "student_group_association". Also it inserts two rows in the table "student_group" and there is no row in the table "student_group_association".

SQL:

/********************** student_group ***************************/

drop table if exists student_group ;

create table student_group
(
  group_id 					varchar(25) not null,
  group_name 				varchar(25) not null,
  group_created_date 			datetime,
  group_created_by 			varchar(25) not null,
  last_modification_date 		datetime,
  learning_style  	varchar(25),
  primary key(group_id)
) TYPE=INNODB;

/*******************************************************************/

insert into table student_group values ( 'DEV','Development','2003-06-06 19:38:02','superadmin','2003-06-06 19:38:02','Expert');
insert into table student_group values ( 'FIN','Finance','2003-06-06 19:32:18','superadmin','2003-06-06 19:32:18','Advanced');

/****************** student_group_association **********************/

drop table if exists student_group_association ;

create table student_group_association
(
  group_id 					varchar(25) not null,
  student_id 				varchar(25) not null,
   
  primary key(group_id,student_id)
) TYPE=INNODB;

/*******************************************************************/
[10 Jun 2003 6:25] Asish Kumar Samanta
Is there any progress?
[10 Jun 2003 8:46] Miguel Solorzano
I have tested your query with the last release 4.0.13 and showed the
expected result, please upgrade and verify the query result:

c:\mysql\bin>mysql test -E
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2 to server version: 4.0.13-nt-log

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> select a.group_id as "Select", a.group_name as "Group Name",
    -> date_format(a.group_created_date,"%M %e, %Y %H:%i") as "Created Date"
    -> date_format(a.last_modification_date,"%M %e, %Y %H:%i") as "Last
    "> Modified", a.learning_style as "Style" ,
    -> count(c.group_id) as "No. of Members" from student_group a left join
    -> student_group_association c on a.group_id = c.group_id
    -> where a.group_id = 'FIN' group by c.group_id, a.group_name, a.group_i
    -> union
    -> select a.group_id as "Select", a.group_name as "Group Name",
    -> date_format(a.group_created_date,"%M %e, %Y %H:%i") as "Created Date"
    -> date_format(a.last_modification_date,"%M %e, %Y %H:%i") as "Last
    "> Modified", a.learning_style as "Style" ,
    -> count(c.group_id) as "No. of Members" from student_group a left join
    -> student_group_association c
    -> on a.group_id = c.group_id
    -> where a.group_id <> 'FIN' group by c.group_id, a.group_name,
    -> a.group_id;
*************************** 1. row ***************************
        Select: FIN
    Group Name: Finance
  Created Date: June 6, 2003 19:32
 Last
Modified: June 6, 2003 19:32
         Style: Advanced
No. of Members: 0
*************************** 2. row ***************************
        Select: DEV
    Group Name: Development
  Created Date: June 6, 2003 19:38
 Last
Modified: June 6, 2003 19:38
         Style: Expert
No. of Members: 0
2 rows in set (0.01 sec)
[3 Jul 2003 5:51] Michael Widenius
Thank you for your bug report. This issue has already been fixed
in the latest released version of that product, which you can download at 
http://www.mysql.com/downloads/