MySQL Bugs: #42453: Column name overriding

Bug #42453	Column name overriding
Submitted:	29 Jan 2009 14:03	Modified:	29 Jan 2009 14:35
Reporter:	Alex P	Email Updates:
Status:	Not a Bug	Impact on me:	None
Category:	MySQL Server: General	Severity:	S3 (Non-critical)
Version:	5.0.51a-community	OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	column name, overriding

Description:
Looks like column name is overridden when two column names are separated by new line and not by comma. For example if i execute this query:

select
   `ad_id`,
   `ad_ca_id`
from 
   `ads`
limit 1

everything is ok. two columns in results are returned:

+-------+--------+
| ad_id |ad_ca_id|
+-------+--------+
|3385482|       0|
+-------+--------+

But if i execute this query (with missing comma between two columns):

select
   `ad_id`
   `ad_ca_id`
from 
   `ads`
limit 1

mysql server doesn't produce error and outputs this:

+--------+
|ad_ca_id|
+--------+
| 3388712|
+--------+

so not only a column is missing, but the result it self is wrong (should be 0)

How to repeat:
Execute query with structure like this one:

select
   `ad_id`
   `ad_ca_id`
from 
   `ads`
limit 1

This is not a bug. Without comma second name is treated as column alias. Please, read http://dev.mysql.com/doc/refman/5.0/en/select.html:

"However, because the AS is optional, a subtle problem can occur if you forget the comma between two select_expr expressions: MySQL interprets the second as an alias name. For example, in the following statement, columnb is treated as an alias name:

SELECT columna columnb FROM mytable;

For this reason, it is good practice to be in the habit of using AS explicitly when specifying column aliases."

ahr.. yes X) didn't intended to use it as alias so run into that problem. Thank you for explain.