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
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