How can I fix this HTACCESS to allow Sub Folder Installation of WP (and it's own htaccess modrewrite rules)

Question

I have a application that uses rewrite conditions, and then I added wordpress. I could not get /blog to rewrite properly.

Please see below for both HTACCESS files in root, and /blog (where wordpress is installed). I need to create a reference in root to allow /blog to work properly (im guessing). But how can I do this without breaking my other rewrite rules?

/.htaccess

RewriteEngine on

RewriteCond %{HTTP_HOST} !^www.example.com$
RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?sn=$1 [QSA,L]
#RewriteRule ^([a-zA-Z0-9/%-]+)$ index.php?sn=$1 [QSA]

Then in wordpress my wordpres install folder, i am simply doing: /blog/.htaccess

#for blog directory only
RewriteEngine On
RewriteBase /blog/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

... and all other rw conditions needed for caching, etc

Answer 1

The reason the error was persistent with this dual HTACCESS setup was because the /blog/.htaccess file was missing an additional line:

RewriteRule . /blog/index.php [L]

Once added, it operated fine. No chances needed to go into the root htaccess to reference the /blog/ rewrite conditions. This allows for a wordpress install in a blog folder, and above references dual HTACESS rules