# Migrations

{% hint style="info" %}
This section is based on [Granite's README](https://mazeframework.gitbook.io/granite)
{% endhint %}

Granite doesn't have migrations built in. Instead, we leveraged the excellent work done by Juan Edi called [micrate](https://github.com/juanedi/micrate). We have integrated Micrate into the Maze CLI.

## Migration scripts

Migration scripts are created in the `db/migrations` directory. It's recommended that the files use a timestamp as a way to keep the order of execution.

A micrate script has two sections, Up and Down. Here is an example file:

```
db/migrations/20171003212124_create_post.sql
```

```sql
-- +micrate Up
CREATE TABLE posts (
  id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
  title VARCHAR(255),
  body TEXT,
  pages INT,
  published BOOL,
  created_at TIMESTAMP NULL,
  updated_at TIMESTAMP NULL
);

-- +micrate Down
DROP TABLE IF EXISTS posts;
```

## Generators

Maze CLI provides the ability to generate migration scripts:

```bash
maze generate migration create_posts
```

This will generate an empty micrate script with the timestamp set in the filename:

```
db/migrations/20171003212124_create_post.sql
```

If you generate a model or scaffold, it will create a migration script that will create and drop the database table.

```bash
maze generate scaffold post name:string body:text pages:int published:bool
```

This will generate the migration script shown above.

## Run the migrations

You can run the migrations using either:

```bash
maze db migrate
```

You can rollback a migration using either:

```bash
maze db rollback
```

## Drop and Create a database

The `maze db` commmand also allows you to create and drop the database itself:

```
maze db drop create migrate
```

## Seed the database

Sometimes you need to pre-populate your tables with data. This is common if you need an beginning administrator account or populate lookup tables that rarely change.

You can do this by creating a `db/seeds.cr` file

```ruby
require "../config/application.cr"

user = User.new
user.email = "admin@example.com"
user.password = "password"
user.save
```

This example `seeds.cr` file creates an admin user.

You can execute the seeds using:

```bash
maze db seed
```


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