If you want to modify database columns etc.

If you want to modify the db: migrated database

I wanted to modify the database while learning team development at a programming school. I missed the knowledge of the details, so I will summarize it for memorandum.

I hope it will be helpful for those who are not familiar with database operations and those who are learning databases in the future.

Development environment

DB:　MySQL Rails: 5.2.4.3

First, check the database (table) you want to modify.

Terminal

% rails db:migrate:status

Then, I think that the tables will come out like this (the number and names of the tables that come out will be different)

Terminal

Status   Migration ID    Migration Name
--------------------------------------------------
   up     20200823051138  Devise create ----s
   up     20200824122031  Create -------s
   up     20200824122659  Add ancestry to ------s
   up     20200824123715  Create -----s
   up     20200829083145  Create -----s
   up     20200906141656  Create -----s I want to modify this table this time
   up     20200907114227  Create -----s
  down    20200927061950  Create -----s
  down    20200927065357  Create -----s
※----Is the table name you created

Pay attention to up and down here.

To fix the migration, the status must be down.

Next, let's bring down the database (table) that you want to modify

To bring it down, run a command like this in your terminal

Terminal

% rails db:rollback

Let's check the status again

Terminal

% rails db:migrate:status

Terminal

Status   Migration ID    Migration Name
--------------------------------------------------
   up     20200823051138  Devise create ----s
   up     20200824122031  Create -------s
   up     20200824122659  Add ancestry to ------s
   up     20200824123715  Create -----s
   up     20200829083145  Create -----s
   up     20200906141656  Create -----s I want to modify this table this time
  down    20200907114227  Create -----s
  down    20200927061950  Create -----s
  down    20200927065357  Create -----s
※----Is the table name you created

that?

Only one down has changed to down.

This is because the rollback command can only be turned down one by one.

So let's try again.

Terminal

% rails db:rollback

Let's check the status again

Terminal

% rails db:migrate:status

Terminal

Status   Migration ID    Migration Name
--------------------------------------------------
   up     20200823051138  Devise create ----s
   up     20200824122031  Create -------s
   up     20200824122659  Add ancestry to ------s
   up     20200824123715  Create -----s
   up     20200829083145  Create -----s
  down    20200906141656  Create -----s I want to modify this table this time
  down    20200907114227  Create -----s
  down    20200927061950  Create -----s
  down    20200927065357  Create -----s
※----Is the table name you created

This time, I was able to bring down the target table safely.

After the correction is finished

This time I wanted to correct the column name, so I changed the column name in the migration file after this.

Finally

Terminal

% rails db:migrate

Let's check the status again

Terminal

% rails db:migrate:status

Terminal

Status   Migration ID    Migration Name
--------------------------------------------------
   up     20200823051138  Devise create ----s
   up     20200824122031  Create -------s
   up     20200824122659  Add ancestry to ------s
   up     20200824123715  Create -----s
   up     20200829083145  Create -----s
   up     20200906141656  Create -----s Modified table
   up     20200907114227  Create -----s
   up     20200927061950  Create -----s
   up    20200927065357  Create -----s
※----Is the table name you created

For the rails db: migrate command, change all down tables to up.

db: migrate is all up at once You can only down db: rollback one by one.

If you want to rollback all at once

I will also introduce a method that can be done collectively when you have to rollback multiple times like this time

Terminal

% rails db:rollback　STEP=2

• By entering STEP = 2, rollback will be executed twice at once.

Once you get used to the rollback command, use the STEP option positively to improve your workability.