# How migrations work?

Once you get into production you'll need to synchronize model changes into the database. Typically, it is unsafe to use `synchronize: true` for schema synchronization on production once you get data in your database. Here is where migrations come to help.

A migration is just a single file with SQL queries to update a database schema and apply new changes to an existing database.

Let's say you already have a database and a `Post` entity:

```
import { Entity, Column, PrimaryGeneratedColumn } from "typeorm"



@Entity()

export class Post {

    @PrimaryGeneratedColumn()

    id: number



    @Column()

    title: string



    @Column()

    text: string

}
```

And your entity worked in production for months without any changes. You have thousands of posts in your database.

Now you need to make a new release and rename `title` to `name`. What would you do?

You need to create a new migration with the following SQL query (PostgreSQL dialect):

```
ALTER TABLE "post" RENAME COLUMN "title" TO "name";
```

Once you run this SQL query your database schema is ready to work with your new codebase. TypeORM provides a place where you can write such sql queries and run them when needed. This place is called "migrations".