Removing content via phpMyAdmin

Hi there, I have an unusual problem.

A recruitment company has been adding jobs for a couple of years now and we're starting to hit some problems. I used a template called jobs.html to add a new content region everytime but they now have over 9,000 jobs in one particular category and now the memory limit has been hit and I cannot delete any to make a bit of space.

I have looked at the tables in the phpMyAdmin but I am at a loss how I can search for them to delete. Below are all the bits of code I think you need.

Can you give me some guidance on where/what I should be looking for to delete amd is there a better way to add jobs to the system so they remove themselves after a particular date to save clogging up the system?

HTML

    <div class="right">
                <?php 
    $opts = array(
            'template'=>'jobs.html',
            'filter'=>'slug',
            'match'=>'eq',
            'value'=>$_GET['s']
        );
    perch_content_custom('Industrial Jobs', $opts); 
?>


    </div>

jobs.html

    <h2><perch:content id="jobtitle" type="text" label="Job Title" html="false" required="true" title="true" /></h2>

    <perch:content id="_id" suppress="true" label="Unique Job Ref ID" required="true" /> 
    <p><strong>Job Type:</strong> <perch:content id="jobtype" type="text" label="Job Type" html="false" required="true" title="false" /><br />
    <strong>Location:</strong> <perch:content id="location" type="text" label="Location" html="false" required="true" title="true" /><br />
    <strong>Salary:</strong> <perch:content id="salary" type="text" label="Salary" html="false" required="false" title="false" /></p>

    <p><strong>Qualifications:</strong> <perch:content id="qualifications" type="text" label="Qualifactions" html="false" required="true" title="false" /><br />
    <strong>Experience:</strong> <perch:content id="experience" type="text" label="Experience" html="false" required="true" title="false" /></p>

    <p><strong>Closing Date: <span class="pink"><perch:content id="date" type="date" label="Closing Date" format="%d %B %Y" required="true" /></span></strong><br />

    <p><strong>Contact Name:</strong> <perch:content id="name" type="text" label="Contact Name" html="false" required="true" title="false" /><br />
    <strong>Phone Number:</strong> <perch:content id="number" type="text" label="Phone Number" html="false" required="true" title="false" /><br />
    <strong>Email:</strong> <a href="mailto:<perch:content id="email" type="text" label="Email" html="false" required="true" title="false" />"><perch:content id="email" type="text" label="Email" html="false" required="true" title="true" /></a></p>

    <div class="apply">
        <a href="mailto:<perch:content id="email" type="text" label="Email" html="false" required="true" title="false" />?subject=<perch:content id="_id" type="text" /> <perch:content id="jobtitle" type="text" /> in <perch:content id="location" type="text" />">APPLY NOW</a>
    </div>

    <h4>More Details</h4>
    <perch:content id="details" type="textarea" label="More Details" textile="false" html="true" editor="ckeditor" />

    <perch:content id="slug" type="slug" for="_id" suppress="true" />