Bug #47483 SELECT UNION wrong length after prepare
Submitted: 21 Sep 2009 14:05 Modified: 21 Sep 2009 19:59
Reporter: Ulf Wendel Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: C API (client library) Severity:S3 (Non-critical)
Version:5.1 OS:Any
Assigned to: CPU Architecture:Any
Triage: Triaged: D3 (Medium)

[21 Sep 2009 14:05] Ulf Wendel
Description:
The C API returns the wrong column length for:

SELECT CAST('one' AS CHAR) AS column1 UNION SELECT CAST('three' AS CHAR) UNION SELECT CAST('two' AS CHAR)

after the prepare stage. It returns 3 although a string of the length 5 will be returned. The real length of 5 is not known before the query has been executed.

Is that a bug or a feature? Please clearify.

The query has caused bug http://bugs.php.net/bug.php?id=45019 . I would like to know if we need to teach PHP users to always call their PHP bind_result() function after execute() if using the MySQL Client Library. 

How to repeat:
Compile attached C demo program.
[21 Sep 2009 14:06] Ulf Wendel
C test program

Attachment: statement_bind.c (text/x-csrc), 3.46 KiB.

[21 Sep 2009 19:59] Sveta Smirnova
Thank you for the report.

Verified as described.