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Serializes a semi-structured value as JSON text.
Syntax
to_json(<expr>)Arguments
| Argument | Type | Description |
|---|---|---|
<expr> | array, object, or any | Value to serialize. Cast a scalar to any first. |
Returns
Returns string. A NULL input returns the string 'null', not a NULL result.
Examples
Serialize a result object for export
Convert a query-built object into JSON text that an application can consume.
VALUES ('checkout', 3)
SELECT $0 AS service, $1 AS failures
SELECT to_json({'service': service, 'failures': failures}) AS json+-------------------------------------+
| json |
+-------------------------------------+
| {"failures":3,"service":"checkout"} |
+-------------------------------------+The result is a string, even though its contents look like an object.
Preserve missing values in JSON
An optional campaign can be missing from an event summary. JSON serialization represents it as JSON null.
SELECT
to_json({'order_id': 'o-17', 'campaign': NULL}) AS json,
to_json(NULL::any) AS missing_payload+-------------------------------------+-----------------+
| json | missing_payload |
+-------------------------------------+-----------------+
| {"campaign":null,"order_id":"o-17"} | null |
+-------------------------------------+-----------------+missing_payload is the string null, not a SQL NULL result.