Suport for JSON is ubiquitous in modern relational database. Since the introduction of JSON support in th SQL:2016 standard, accessing (nested) JSON values is very similar across database products using SQL/JSON path expressions.
PostgreSQL was the first relational database to support JSON and corresponding JSON functions. With version 12 it also supports SQL/JSON path.
For certain types of conditions, the PostgreSQL specific operators and functions are more powerful than the SQL/JSON path functions.