Most in cases, phpmyadmin not allows to import your database if you have a large mysql database with .sql extension. At this moment , you can easily import your database to mysql by using windows cmd or any terminal. In this post , we use windows cmd.
First open a command prompt and you need to goto the exact mysql installation path/bin . if you are using xampp installation, the path would be C:\xampp\mysql\bin
cd C:\xampp\mysql\bin
and lets copy your .sql file , where the database you need to import. lets say mydb.sql.
Then run the following command to import your database
mysql -u username -pPlainPassword databasename < filename.sql
example:
mysql -u USER -p123 wp_users < mydb.sql