Database: One table or many I am working on a project of classified ads site.

I have 12 main categories, and their items are 142, Like vehicles have cars, scooters, bikes, etc. Mobiles Phones have mobiles, tablets, accessories.

Now should i use few tables and use Json ?

Or should i create separate tables for each item (142 tables) ?

Currently i have decided 142 tables to save myself from relations and joins and heavy coding.

Which way is correct or suggest another one. What are the pros and cons ? I have search a lot but didn't got anything that answers my question.
You should definitely (in my opinion) not have 142 tables - it'll be a complete mess to name, index and maintain, and you'll generate yourself a lot of extra work if you some day add another category, if you need to move ads from one category to another, etc.

Storing JSON blobs in the database will kill performance when you're performing searches, so I wouldn't go with that either.

A good relational table design (yes, with joins) is really the best approach when you're using a relational database system. For instance, one table with categories (12 records), joined to one table with items (142 records), joined to a table of ads.