Firebase : How to check if a User ID already Exist

[developer_calife (Himanshu)]

I have made a review system so that users can post reviews about my products in my app, and I have used Firebase to store User ID.

The User ID is a bucket and it contains name and tags of differnt products, shown below

But the reviews are stored in Airtable and called from there, I am trying that 1 user must post one review, how to check if User ID already exist in firebase, or how to check the Bucket with “User ID” is already created

[David (‎ David Ningthoujam)]

First grab the tags and compare with the username

[developer_calife (Himanshu)]

but the User Id is the bucket, it is not a tag

[Alapjeet (Alapjeet Singh)]

this screenshot will be helpful
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[David (‎ David Ningthoujam)]

can you try please?

[Alapjeet (Alapjeet Singh)]

the blocks i upload. if it is in tag then also & if it in value then also you can get…