JSON集計関数

JSON Aggregation Functions

The integration is bidirectional. The database doesn't have to limit itself to parsing JSON: it can build it. Imagine if your API and Node.js didn't have to do the dirty, intensive work of serializing nested objects into JSON, because the DB delivered them already built straight from disk.

Building Objects and Arrays

Instead of the classic mass aggregation or string concatenation (String_agg), we turn to these functions:

• json_build_object(key, value, ...) or jsonb_build_object(...)
• json_agg(...) or jsonb_agg(...)

SELECT json_build_object('name', first_name, 'city', city) AS data
FROM customers;

You'll see rows printed containing { "name": "...", "city": "..." }, perfectly compliant.