JSON & JSONB

Store and query semi-structured data — a job-critical Postgres skill.

Semi-structured data

jsonb stores JSON in an efficient binary form you can index and query. Each book has an attributes jsonb like {"format":"hardcover","pages":320}. Reach inside it:

attributes->'pages' — get the value as jsonb
attributes->>'format' — get it as text (note the double >)
(attributes->>'pages')::int — text, then cast to a number
attributes @> '{"format":"ebook"}' — containment (GIN-indexable, fast)

SELECT title FROM books WHERE attributes @> '{"format":"ebook"}';

Every row here reads the same stored value, {"format":"hardcover","pages":320} on The Glass Forest. The single arrow keeps you inside jsonb (so 320 is still a JSON number); the double arrow exits to text, which is why comparing pages to a number needs the cast.