For mySQL trigger, need to set field value to selected value - mysql

Question

I'm building a Joomla website for a homeowner's association. When a user makes a payment, I want the mySQL jos_Payments table (where the payment gets saved) to automatically grab the ID for the home that user lives in.
I've created a trigger on the jos_Payments table, BEFORE INSERT. I'm trying to set the home_id field of the newly added row to be equal to the cb_home_id value that is looked up in the jos_comprofiler table.
SET NEW.home_id = (SELECT cb_home_id FROM jos_comprofiler WHERE jos_comprofiler.user_id = NEW.user_id);
I've searched for help on this, and have tried defining a variable as an intermediate step, and none of it seems to help. It just keeps telling me I have an error in my SQL syntax. The SELECT statment works outside of the trigger, if I use a valid user_id instead of NEW.user_id.
It seems like this should be so simple. Where am I going wrong?

Answer 1

I presume the code sample is part of that BEFORE INSERT trigger which fails creation.
I had a simular issue with Joomla 2.5, unable to create a trigger during the install or update procedure while the sql statements work fine.
You will not be able to create a trigger, function, procedure or any sql statement containing more than 1 semi-colon (;). That's why all other statements seem to work in your script.
I tried many appoaches which did not work including these:
In the manifest file use sql-file:
<install>
<sql>
<file driver="mysql" charset="utf8">sql/install.mysql.utf8.sql</file>
</sql>
</install>
In the manifest file use install-queries:
<install>
<queries>
<query id="1">
CREATE TRIGGER `...` AFTER UPDATE ON `#__...` FOR EACH ROW
BEGIN
...codeline...;
...codeline...;
END
</query>
<query id="2">
...
</query>
</queries>
</install>
(sorry for using blockquotes in stead of code sample, otherwise post will not be shown correctly)
The only way it did work was via the installscript option available since Joomla 2.5, see https://docs.joomla.org/J2.5:Developing_a_MVC_Component/Adding_an_install-uninstall-update_script_file.
This did not work out-of-the-box. I had to remove the access check (the first line with define) and put the following code in the install($parent) and update($parent) functions to add the trigger:
$db = JFactory::getDbo();
$db->setQuery("DROP TRIGGER IF EXISTS `...`");
$db->query();
$query="CREATE TRIGGER `...` AFTER UPDATE ON `#__...` FOR EACH ROW
BEGIN
...codeline...;
...codeline...;
END";
$db->setQuery($query);
$db->query();
if ($error = $db->getErrorMsg()) {
$this->setError($error);
return false;
}
...next sqlstatement or code...
return true;
Make sure the classname in this installer php file matches your component name including init caps, something like:
class com_YourComponentNameInstallerScript
And also, don't forget to open the file with <?php tag but do not put the ?> end tag at the end.
Save the file as php file in the root of your install package at the same level as the manifest file, and add this filename to the manifest file at somewhere between the component description and administration or site tags:
<scriptfile>yourcomponentname_install.php</scriptfile>
This method will also work with creating Stored Procedures and Functions.