How to defragment or optimize a database in Mysql?

In case you remove a lot of data from the tables OR change the database structure, a de-fragmentation/optimizing of the database is necessary to avoid performance loss, especially while running queries. The above changes results in a performance loss, so make sure you run the “optimizer” on the database.
SSH to your server and execute:

mysqlcheck -o 

where, -o stands for optimize which is similar to defragmentation. You should look to defragment the tables regularly when using VARCHAR fields since these coloumns get fragmented too often.