Merging WordPress installations following site upgrades in an isolated development environment

wordpress_migration

When developing a WordPress site in a development environment with an existing 
production environment serving live traffic, updates need to be merged back 
into the production environment. With major upgrades, this can involve both 
codebase and database changes. While WordPress excels in providing a simple 
way to introduce new functionality easily by installing plugins, the absence 
of database schema migration scripts makes it difficult to deploy changes to 
an existing installation. 

As the production site typically has content being added to it which needs to 
be preserved while the development site may have schema changes, it's necessary 
to retain the content tables while updating all other tables. This could be due 
to updating WordPress itself, updating plugins, installing new plugins, applying 
new settings or introducing custom tables. It's possible to take the following 
tables from the production database and merge them into the development version, 
resulting in an updated installation with the most current content:

# Articles (posts, pages, custom posts) and metadata
TRUNCATE wp_postmeta;
TRUNCATE wp_posts;

# Comments and associated metadata
TRUNCATE wp_commentmeta;
TRUNCATE wp_comments;

# User login information and associated metadata
TRUNCATE wp_users;
TRUNCATE wp_usermeta;

# Taxonomy related data (categories and tags)
TRUNCATE wp_terms;
TRUNCATE wp_term_relationships;
TRUNCATE wp_term_taxonomy;

# Links (deprecated but may still exist in older installations)
TRUNCATE wp_links;

After clearing these tables, content from the production environment can be 
inserted into them.

More information about the WordPress database structure can be found here:
https://codex.wordpress.org/Database_Description