4. SQL Query
I ♥ Sequel Pro
via phpMyAdmin or a database client
UPDATE wp_posts SET post_content =
REPLACE (post_content,
'Item to replace here',
'Replacement text here');
I originally saw this code on lorelle.wordpress.com
5. Or a plugin!
Options to change
•post & page content
•excerpts
•attachments
•custom fields
•all GUIDs