Question

I recently posted a question about connecting two queries to omit elements found in a second:

MYSQL – How to join two queries to omit elements found in the second query (or perhaps any better solution?)

Now I am wondering how to look at a number of meta_keys and their corresponding values to achieve something else.

I am essentially building an event system with custom fields, simplified, an event will have:

• Start Date
• End Date
• Ongoing (Yes or No)

These are stored as

-----------
wp_postmeta
-----------
meta_key
meta_value
post_id

e.g.

-----------
wp_postmeta
-----------
Start Date
2011-07-30
10

-----------
wp_postmeta
-----------
End Date
2011-08-30
10

-----------
wp_postmeta
-----------
Ongoing
Yes
10

My confusion lies in trying to look at multiple wp_postmeta entries and connecting them with the appropriate post.

For example, I want to find the posts that:

• Start Date > Today
• End Date > Today
• Ongoing = Yes

Building upon the previous question, I am trying this query:

SELECT * FROM wp_posts, wp_postmeta
WHERE wp_posts.ID = wp_postmeta.post_id

AND wp_posts.ID IN (
SELECT post_id FROM wp_postmeta
WHERE wp_postmeta.meta_key = 'Start Date'
AND wp_postmeta.meta_value > NOW())

AND wp_posts.ID IN (
SELECT post_id FROM wp_postmeta
WHERE wp_postmeta.meta_key = 'Ongoing'
AND wp_postmeta.meta_value = 'Yes')

AND wp_posts.ID IN (
SELECT post_id FROM wp_postmeta
WHERE wp_postmeta.meta_key = 'End Date'
AND wp_postmeta.meta_value > NOW())

Which is not really working.

I feel like there must be a way to find all the related meta_keys and join their values to the post table, so it can be more easily accessed. For example, is it possible to find the meta_value for ‘Start Date’ and join it to the wp_posts with a column title start_date_value or something like that?

Or how should I be approaching this problem instead?

---

Using the answer from @karevn, I came up with the following code which works exactly as I want:

$query = array(
        'category_name' => 'event',
        'meta_query' => array(
            'relation' => 'AND',
            array(
                'key' => 'Start Date',
                'value' => $today,
                'compare' => '>'
            ),
            array(
                'key' => 'End Date',
                'value' => $today,
                'compare' => '>'
            ),
            array(
                'key' => 'Ongoing',
                'value' => 'Yes',
                'compare' => '='
            ),
        )
    );

I think this is a pretty powerful feature of wordpress.

Answer 1

You can use WP_Query class with meta_query option and avoid writing your own SQL at all. See Codex: http://codex.wordpress.org/Class_Reference/WP_Query#Custom_Field_Parameters. It is supposed to be a better way in WordPress. Your query will look pretty much like this then:

$query = new WP_Query(array('meta_compare' => array(
    array('key' => 'Start Date', 'compare' => '>', 'type' => 'DATE', 'value' => $today),
    array('key' => 'End Date', 'compare' => '>', 'type' => 'DATE', 'value' = $today),
    array('key' => 'Ongoing', 'value' => 'Yes')));

The side effect of using this code is that its results may be cached by DB caching plugin.