[RAILS] Relationship between database and model (basic)

About files related to the database

Purpose: I wrote this article because I thought that I had to understand the difference between the roles of model files and migration files in order to resolve errors.

Currently: We are in the final stage of portfolio creation, but there are still many things we do not understand, and we realize that we do not have enough basic understanding, and we are understanding from the mechanism while solidifying the basics.

Role of model file

This file shows the access authority to the database.
The model and association described indicate the access authority to the database through the model.

Why can't I retrieve this data? To understand, look at the model file that describes the access rights to the database. And it is the first step towards understanding.

Role of migration file

A file that describes the information required to store the contents of the data.
When passing data, specify the table name (class) and column name described in the file.

Why specify the table name (class)?

• If you want to store information that matches the column conditions, you must specify the class and then the column name when retrieving the stored data.
  If you replace it with your daily life, you will end up in a situation where you are "screaming Mr. Yamada in front of the whole" instead of saying "Mr. Yamada in the XX class". 　

Summary

Understand both together

You will be able to understand the basics of how data is received from the database.

• Model file: Do you have database privileges for the data you want to use?
• Migration file: What information does the table stored in the database hold?

Unrelated models and models

• You need to create a relation because you cannot exchange between databases.
• You need to retrieve each data and create an instance variable.

Incidentally

Understanding the MVC phase

• model: Get data, store data, get data, pass data
• controller: Get information from view/model, pass information that view/model wants to get, pass information that view/model wants to get
• view: Get model information from controller

Advantages (impressions) of publishing the output

Do you really understand yourself? By writing while thinking many times, I was able to establish my knowledge.
Also, I don't know if it was a useful article for someone, but by publishing it on my blog, I was able to deeply understand and train my ability to communicate.
Thank you to everyone who read it.
If you have any mistakes, please do not hesitate to comment.