GROUP_CONCAT之后具有WHERE子句的Wordpress MySQL查询返回意外结果

Question

            SELECT p.*,
        GROUP_CONCAT(pm.meta_key ORDER BY pm.meta_key DESC SEPARATOR '||') as meta_keys, 
        GROUP_CONCAT(pm.meta_value ORDER BY pm.meta_key DESC SEPARATOR '||') as meta_values
        FROM $wpdb->posts p 
        LEFT JOIN $wpdb->postmeta pm on pm.post_id = p.ID 
        WHERE p.post_type = 'item' and p.post_status = 'publish' 
        AND pm.meta_key = 'adtype' 
        AND pm.meta_value = '1'
        GROUP BY p.ID
        ORDER BY p.post_date_gmt DESC
        LIMIT 0,10

I'm using a special WordPress query to get post and postmeta data and ran into a problem when I wanted to add an additional WHERE on the postmeta.

Here I want to limit results where pm.meta_key adtype is equal to 1. The query works, but var_dump() shows that it changes the value of the group concatenated meta_keys and meta_values.

In my results I no longer get meta_keys and meta_values out as concatenated results, rather they get set to the WHERE values of 'adtype' and '1' respectively.

The query works without the additional WHERE clauses, but I would like the ability to filter results.

Answer 1

It's normal, when you add the WHERE clause :

    AND pm.meta_key = 'adtype' 
    AND pm.meta_value = '1'

you are limiting the result to only the rows that have these values, so in your meta_keys & meta_values your won't have values that differ from those specified in the WHERE clause.

Answer 2

I found the solution myself in this thread: Can't get a complicated mysql query to work

In the SELECT statement I gave a new value for adtype with:

max(case when pm.meta_key='adtype' then pm.meta_value end) as adtype

And after GROUP BY I added:

HAVING adtype = '1'

This worked!