如何在mysql中获取关系表中的项数

i have two mysql db tables 'tags' and 'tags_used'. i have added images for checking the db structure.currently iam using laravel fluent query builder. Now what i want to query is the count of rows in relation table like below. Please help me with either laravel fluent query or plain sql query.i have two mysql db tables 'tags' and 'tags_use