Select value of jsonb column in PostgreSQL

The shortest version would be:

SELECT DISTINCT value->'Tag' AS tag
FROM Documents, jsonb_array_elements(Documents.Tags);

The jsonb_array_elements() function unnests the JSONB array into a set of rows with a single column called "value". It uses an implicit "lateral join" on the Documents table.

This gives you the distinct tags as jsonb values. If you want them as a text value, use the ->> operator instead of ->.

you can also use the following snippet.

SELECT 
  id, 
  data::json->'name' as name
FROM books;