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_examples/real-world-examples/synchronizing-databases/README.md

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+# Synchronizing Databases (MySQL to PostgreSQL)
+
+This example shows how to use [SQL Pub/Sub](https://github.com/ThreeDotsLabs/watermill-sql) across two different databases.
+
+See also [SQL Pub/Sub documentation](https://watermill.io/pubsubs/sql).
+
+## Background
+
+Synchronizing two databases can be a tough task, especially with different data formats.
+This example shows how to migrate a MySQL table to PostgreSQL table using watermill.
+
+The application will first transfer all existing rows and then keep listening for any new inserts,
+copying them to the new table as soon, as they appear. Only new rows will be detected, there's no
+support for updates or deletes.
+
+The `main.go` file contains watermill-related setup, database connections and the handler translating events
+from one format to another. In `mysql.go` and `postgres.go` you will find definitions of `SchemaAdapters` for 
+each database.
+
+For more detailed description, see [When an SQL database makes a great Pub/Sub](https://threedots.tech/post/when-sql-database-makes-great-pub-sub/).
+
+## Requirements
+
+To run this example you will need Docker and docker-compose installed. See installation guide at https://docs.docker.com/compose/install/
+
+## Running
+
+Run the command and observe standard output. It should print out incoming users.
+
+```bash
+docker-compose up
+```
+
+Check what's inside MySQL by running:
+
+```
+docker-compose exec mysql mysql -e 'select * from watermill.users;'
+```
+
+```
++----+------------------+------------+-----------+---------------------+
+| id | user             | first_name | last_name | created_at          |
++----+------------------+------------+-----------+---------------------+
+|  1 | Carroll8506      | Marc       | Murphy    | 2019-09-28 13:51:53 |
+|  2 | Metz8415         | Briana     | Bauch     | 2019-09-28 13:51:54 |
+|  3 | Lebsack6887      | Tomasa     | Steuber   | 2019-09-28 13:51:55 |
+|  4 | Hauck4518        | Alexandra  | Halvorson | 2019-09-28 13:51:56 |
+|  5 | Reynolds7156     | Ariane     | Lebsack   | 2019-09-28 13:51:57 |
++----+------------------+------------+-----------+---------------------+
+```
+
+And the same for PostgreSQL:
+
+```
+docker-compose exec postgres psql -U watermill -d watermill -c 'select * from users;'
+```
+
+```
+ id  |     username     |      full_name       |     created_at
+-----+------------------+----------------------+---------------------
+   1 | Carroll8506      | Marc Murphy          | 2019-09-28 13:51:53
+   2 | Metz8415         | Briana Bauch         | 2019-09-28 13:51:54
+   3 | Lebsack6887      | Tomasa Steuber       | 2019-09-28 13:51:55
+   4 | Hauck4518        | Alexandra Halvorson  | 2019-09-28 13:51:56
+   5 | Reynolds7156     | Ariane Lebsack       | 2019-09-28 13:51:57
+```