It usually requires large queries to get the desired data from WordPress database. Times it requires lot of joins as multiple tables are used. Is there any hack to get the data from wordpess database while avoiding long queries.
You could create views to encapsulate the long/complicated queries; for syntax and examples check this: https://dev.mysql.com/doc/refman/5.7/en/create-view.html.
Have you got a wordpress site with so much content that it matters? Joins etc just mean the design is right and are nothing to be afraid of. Can you give us an example of a query that is slowing your site down?
The query to find out the sales of specific brand in specif area required me to join 5 different tables. Is there any plugin or any means of doing this without writing long queries. I am using mysql DB.
Joining 5 tables is absolutely fine. A plugin is still going to do the join. If you give us the sql for the query we might be able to understand your concerns a bit better.
If you need data that's scattered among 5 tables, you're going to have to SELECT on 5 tables, there's no other way. There may be some code that you can give the table and field names to, and it will return the data for you, but the part you write is still going to be almost as long. That's just the way SQL works. The only "plugin" that would shorten the query would be one that's already written for those tables and fields, and you just call it - but if you need queries on different sets of fields and/or tables, it's going to be shorter to write each one individually.