In case you are are using Yoast plugin for SEO and using it to enter meta post description, you can query meta descriptions of all posts stored in custom field _yoast_wpseo_metadesc. This may be handy to bulk review the meta descriptions of all your posts and pages. Here are some queries to get custom field _yoast_wpseo_metadesc for all posts:
_yoast_wpseo_metadesc meta values for all posts
This query will display null in case _yoast_wpseo_metadesc meta_value does not exist.
SELECT p.ID, p.post_title, pm.meta_key, pm.meta_value
FROM wp_posts p
LEFT JOIN wp_postmeta pm ON p.ID = pm.post_id AND pm.meta_key = '_yoast_wpseo_metadesc'
WHERE p.post_type in ('post', 'page')
AND p.post_status='publish'
Posts with null _yoast_wpseo_metadesc meta value
This query will display all post where _yoast_wpseo_metadesc meta value does not exist.
SELECT p.ID, p.post_title, pm.meta_key, pm.meta_value
FROM wp_posts p
LEFT JOIN wp_postmeta pm ON p.ID = pm.post_id AND pm.meta_key = '_yoast_wpseo_metadesc'
WHERE p.post_type in ('post', 'page')
AND p.post_status='publish'
AND pm.meta_key IS NULL
Note these queries can be used to find meta value for other meta keys after slight modification.
