Test queries with a database branch

In the previous example, a DELETE query was executed on the elements table to remove duplicates, but the problematic query deleted most of your data.

Since a DELETE query is a potentially destructive operation, it is recommended that you test DELETE queries before you run them on your production database to make sure they work as intended. You can do this easily in Neon by creating a test branch.

Navigate to the Branches page and click on the New Branch button to create a new branch. Name the branch test_branch.

This time, create the branch from Head, which creates a branch with the most up-to-date state of your database. Specify the recovery branch you created previously as the parent branch.

Test your query

Navigate to the SQL Editor, select the test branch, and run your new DELETE query.

DELETE FROM elements
WHERE (id, elementName, atomicNumber, symbol) IN (
  SELECT id, elementName, atomicNumber, symbol
  FROM elements
  GROUP BY id, elementName, atomicNumber, symbol
  HAVING COUNT(*) > 1
);

Next, run the following query to verify that the query ran as intended:

SELECT * FROM elements ORDER BY id;

You find that the query successfully removed duplicates from the elements table. You can now safely apply the query to your production branch, and the test branch can be deleted.

Conclusion

Congratulations. You completed the Neon tutorial. Here is a recap of what was covered:

• You learned how to create a Neon project.
• You created a table and inserted data using the Neon SQL Editor.
• You learned about Neon's database branching feature and how you can use it to recover lost data
• You learned how you can use branches to test potentially destructive queries before before running them in production.