what does $${}$$::json in Postgres mean?

data jsonb NOT NULL DEFAULT $${}$$::jsonb what does $${}$$ on table creation? Can’t find anything on the internet. Thanks

>Solution :

In Postgres $$ (or $anything$) is an alternative for a single quotation mark (') to enclose character literals. In other words, $${}$$ is equivalent to '{}'.

It’s commonly used to quote strings that themselves might contain single quotation marks, or strings inside dynamic SQL that is already enclosed in single quotes.

Reference