Re: [xsl] A MySQL heads-up.

[Paul DuBois <paul@xxxxxxxxxxxx>]

At 18:21 -0500 12/2/03, Ben Trafford wrote:
> 	Just a wee heads-up for anybody using MySQL's XML output 
> function...it seems to export any empty field with a datatype of 
> "text" as an empty element, rather than an element containing the 
> NULL one might expect.

Why do you expect this?  An empty field is not the same as a field that
contains NULL.

I issued these statements using mysql -X:

DROP TABLE IF EXISTS t;
CREATE TABLE t (tx TEXT);
INSERT INTO t (tx) VALUES(''),(NULL),('some text');
SELECT tx FROM t;

The result was:

<?xml version="1.0"?>

<resultset statement="SELECT tx FROM t">
  <row>
        <tx></tx>
  </row>

  <row>
        <tx>NULL</tx>
  </row>

  <row>
        <tx>some text</tx>
  </row>
</resultset>


Dumping the table with mysqldump -X produces:

<?xml version="1.0"?>
<mysqldump>
<database name="test">
        <table name="t">
        <row>
                <field name="tx"></field>
        </row>
        <row>
                <field name="tx">NULL</field>
        </row>
        <row>
                <field name="tx">some text</field>
        </row>
        </table>
</database>
</mysqldump>


In both cases, the output for the empty value and the NULL value are
different.  If they were not, you'd be hard-pressed to distinguish
the two in your stylesheets.  (Of course, as it is, you can't really
distinguish NULL from a column containing the string "NULL", hm....)

> 	I found this out a few minutes ago, after a very frustrating 
> search. If you've encountered this, you might think your XSLT was 
> broken, as I did. Never fear! It's the product!
>
> 	;^)
>
> --->Ben


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