Change the domain name 301 Jump Related issues

Help change domain name 301 Jump question
Suppose old domain name: a.com, new domain name: B.Com

Ask how to configure the. htaccess, the original domain name all URL 301 to the new domain name, including the level two domain name
such as: www.a.com-www.b.com
A.com-www.b.com
Shop.a.com-shop.b.com
Photo.a.com-photo.b.com
...................... Wait a minute

I've added the following rules to the. htaccess, which will turn all URLs to www.b.com and not meet the requirements

Rewriteengine on
Rewritebase/
Rewritecond%{request_filename}!-f
Rewritecond%{request_filename}!-d

Rewritecond%{http_host} (. *) a.com [NC]
Rewriterule ^ (. *) $ http://www.b.com/$1 [R=301,NC]


Note: Server environment Apache + PHP

------Solution--------------------
You try to add the following:

Rewriteengine on
Rewritecond%{http_host} ^[^\.] +\.a\.com$
Rewriterule ^ (. *)%{http_host}/$1 [C]
Rewriterule ^ ([^\.] +) \.a\.com (. *) $ http://$1\.b\.com$2\?%{query_string} [r=301,l]

It's not a good idea to add a/.

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