Delete Tags from WordPress that have no posts -- http://www.makeuseof.com/tag/7-wordpress-database-queries-search-blog/

delete-unused-tags.sql

SELECT name, slug 
FROM wp_terms
WHERE term_id
IN (
SELECT term_id
FROM wp_term_taxonomy
WHERE taxonomy='post_tag'
AND count='0'
);



DELETE FROM wp_terms
WHERE term_id
IN (
SELECT term_id
FROM wp_term_taxonomy
WHERE taxonomy='post_tag'
AND count='0'
);

find-posts-by-author-id.sql

SELECT ID, post_title
FROM wp_posts
WHERE post_status = 'publish'
AND post_author = 11;

gistfile1.txt

SELECT ID, POST_TITLE
FROM wp_posts
WHERE post_content LIKE '%src=%'
AND post_status = 'publish'
LIMIT 100;

gistfile2.txt

SELECT ID, POST_TITLE
FROM 'wp_posts'
WHERE 'post_type' = 'post'
AND 'post_date' > '2009-04-15 08:00:00'
AND 'post_date'< '2009-04-30 08:00:00'
LIMIT 100;

gistfile3.txt

SELECT p.id as post_id, u.user_nicename as author, p.post_title, p.post_name as post_slug, p.post_date as local_publish_date, p.comment_count 
FROM wp_posts p, wp_users u 
WHERE p.post_status='publish' 
AND p.post_type='post' 
AND u.id = p.post_author 
ORDER BY p.post_date DESC 
LIMIT 500;