Extract a selected file from tar.gz files

First unzip the file using

gunzip filename.tar.gz

This create a filename.tar file then to display the contets use

tar -t filename.tar

Then if you want to extract a file called abc.sql from that tar just give the command

tar -xvf /path/filename.tar -M /fullpath/abc.sql

It will be extracted to /fullpath/inside/abc.sql in the directory you are residing.