At 11:35 +1300 11/11/04, Toro Hill wrote:
>Hi all.
>I have question about how the function quote() works with NULL
>values. Here is what the mysql manual say:
>---
>QUOTE(str)
>Quotes a string to produce a result that can be used as a properly
>escaped data value in an SQL statement. The string is returned
>surrounded by single quotes and with each instance of single quote
>(`''), backslash (`\'), ASCII NUL, and Control-Z preceded by a
>backslash. If the argument is NULL, the return value is the word
>``NULL'' without surrounding single quotes. The QUOTE() function was
>added in MySQL 4.0.3.
>
>mysql> SELECT QUOTE('Don\'t!');
> -> 'Don\'t!'
>mysql> SELECT QUOTE(NULL);
> -> NULL
>---
>Now after reading this I thought that select quote(NULL) would
>return the string 'NULL' (without quotes) and not the NULL value.
>However, this is not true on the version of mysql that I'm using:
>
>mysql> select version();
>+---------------------+
>| version() |
>+---------------------+
>| 4.0.22-standard-log |
>+---------------------+
>1 row in set (0.00 sec)
>
>mysql> select isnull(quote(NULL));
>+---------------------+
>| isnull(quote(NULL)) |
>+---------------------+
>| 1 |
>+---------------------+
>1 row in set (0.01 sec)
>
>mysql> select isnull(quote('not null'));
>+---------------------------+
>| isnull(quote('not null')) |
>+---------------------------+
>| 0 |
>+---------------------------+
>1 row in set (0.00 sec)
>
>So I guess I'm just confused by the documentation. It's easy enough
>to get the string 'NULL' by using select ifnull(quote(NULL), 'NULL')
>or something similiar.
>
>Based on the functionality I experienced I thought that the
>documentation should read something like:
>---
>QUOTE(str)
>... If the argument is NULL, the return value is NULL. ...
>---
>
>Does this seem correct? Have I missed or overlooked something?
No, I think this is a bug. QUOTE(NULL) should return a string,
not a NULL value. I've filed a bug report:
http://bugs.mysql.com/bug.php?id=6564
--
Paul DuBois, MySQL Documentation Team
Madison, Wisconsin, USA
MySQL AB, www.mysql.com
