How to get size of mysql database?

How to get size of a mysql database?
Suppose the target database is called "v3".

Answer

Run this query and you'll probably get what you're looking for:

SELECT table_schema "DB Name",
        ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) "DB Size in MB" 
FROM information_schema.tables 
GROUP BY table_schema; 

This query comes from the mysql forums, where there are more comprehensive instructions available.