Postgres JSON_QUERY() Function

Summary: JSON_QUERY(), added in PostgreSQL 17, extracts JSON or JSONB fragments using SQL/JSON path expressions and returns jsonb. Unlike JSON_VALUE(), it supports multi-value results through WITHOUT, WITH CONDITIONAL, and WITH UNCONDITIONAL WRAPPER modes. Use it when a query must return a JSON object or array rather than a scalar, or when you need OMIT QUOTES, PASSING variables, or ON EMPTY / ON ERROR fallback behavior. It accepts any JSON or JSONB input, supports a RETURNING clause for type conversion, and raises SQLSTATE 22034 when multiple values are returned without a wrapper.

Postgres JSON_QUERY() Function

Extract and Transform JSON Values with SQL/JSON Path Expressions

The JSON_QUERY() function introduced in PostgreSQL 17 provides a powerful way to extract and transform JSON values using SQL/JSON path expressions. This function offers fine-grained control over how JSON values are extracted and formatted in the results.

Use JSON_QUERY() when you need to:

Extract specific values from complex JSON structures
Handle multiple values in results
Control JSON string formatting
Handle empty results and errors gracefully

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Function signature

The JSON_QUERY() function uses the following syntax:

SQL

JSON_QUERY(
    context_item,                    -- Input JSON/JSONB data
    path_expression                  -- SQL/JSON path expression
    [ PASSING { value AS varname } [, ...] ]
    [ RETURNING data_type [ FORMAT JSON [ ENCODING UTF8 ] ] ]
    [ { WITHOUT | WITH { CONDITIONAL | [UNCONDITIONAL] } } [ ARRAY ] WRAPPER ]
    [ { KEEP | OMIT } QUOTES [ ON SCALAR STRING ] ]
    [ { ERROR | NULL | EMPTY { [ ARRAY ] | OBJECT } | DEFAULT expression } ON EMPTY ]
    [ { ERROR | NULL | EMPTY { [ ARRAY ] | OBJECT } | DEFAULT expression } ON ERROR ]
) → jsonb

Understanding Wrappers and Quotes

Wrapper Behavior

By default, JSON_QUERY() does not wrap results (equivalent to WITHOUT WRAPPER). There are three wrapper modes:

WITHOUT WRAPPER (default):
- Returns unwrapped values
- Throws an error if multiple values are returned
WITH UNCONDITIONAL WRAPPER (same as WITH WRAPPER):
- Always wraps results in an array
- Even single values are wrapped
WITH CONDITIONAL WRAPPER:
- Only wraps results when multiple values are present
- Single values remain unwrapped

Quote Behavior

For scalar string results:

By default, values are surrounded by quotes (making them valid JSON)
KEEP QUOTES: Explicitly keeps quotes (same as default)
OMIT QUOTES: Removes quotes from the result
Cannot use OMIT QUOTES with any WITH WRAPPER option

Example usage

Let's explore these behaviors using a sample dataset:

SQL

CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    data JSONB
);

INSERT INTO users (data) VALUES
('{
    "profile": {
        "name": "John Doe",
        "contacts": {
            "email": ["john@example.com", "john.doe@work.com"],
            "phone": "+1-555-0123"
        }
    }
}');

Working with single values

SQL

-- Default behavior (unwrapped, quoted)
SELECT JSON_QUERY(
    data,
    '$.profile.contacts.email[0]'
) FROM users;

text

# |        json_query
------------------------
1 | "john@example.com"

SQL

-- With unconditional wrapper
SELECT JSON_QUERY(
    data,
    '$.profile.contacts.email[0]'
    WITH WRAPPER
) FROM users;

text

# |        json_query
------------------------
1 | ["john@example.com"]

Working with multiple values

SQL

-- Must use wrapper for multiple values
SELECT JSON_QUERY(
    data,
    '$.profile.contacts.email[*]'
    WITH WRAPPER
) FROM users;

text

# |                        json_query
-----------------------------------------------------
1 | ["john@example.com", "john.doe@work.com"]

SQL

-- This will error (multiple values without wrapper)
SELECT JSON_QUERY(
    data,
    '$.profile.contacts.email[*]'
    ERROR ON ERROR
) FROM users;

text

ERROR: JSON path expression in JSON_QUERY should return single item without wrapper (SQLSTATE 22034)
HINT: Use the WITH WRAPPER clause to wrap SQL/JSON items into an array.

Using conditional wrapper

SQL

-- Single value with conditional wrapper
SELECT JSON_QUERY(
    data,
    '$.profile.contacts.phone'
    WITH CONDITIONAL WRAPPER
) FROM users;

text

# |     json_query
-------------------
1 | "+1-555-0123"

SQL

-- Multiple values with conditional wrapper
SELECT JSON_QUERY(
    data,
    '$.profile.contacts.email[*]'
    WITH CONDITIONAL WRAPPER
) FROM users;

text

# |                        json_query
-----------------------------------------------------
1 | ["john@example.com", "john.doe@work.com"]

Quote handling

SQL

-- Default (quoted)
SELECT JSON_QUERY(
    data,
    '$.profile.contacts.phone'
) FROM users;

text

# |     json_query
-------------------
1 | "+1-555-0123"

SQL

-- Without quotes (must not use with wrapper)
SELECT JSON_QUERY(
    data,
    '$.profile.contacts.phone'
    RETURNING TEXT
    OMIT quotes
) FROM users;

text

# | json_query
-------------
1 | +1-555-0123

Using the PASSING clause

SQL

-- Extract array element using a variable
SELECT JSON_QUERY(
    '[1, [2, 3], null]',
    'lax $[*][$idx]'
    PASSING 1 AS idx
    WITH CONDITIONAL WRAPPER
);

text

# | json_query
-------------
1 | 3

Handling empty results

SQL

-- Return custom value when path doesn't match
SELECT JSON_QUERY(
    '{"a": 1}',
    '$.b'
    DEFAULT '{"status": "not_found"}' ON EMPTY
);

text

# |           json_query
--------------------------------
1 | {"status": "not_found"}

SQL

-- Return empty array when path doesn't match
SELECT JSON_QUERY(
    '{"a": 1}',
    '$.b[*]'
    EMPTY ARRAY ON EMPTY
);

text

# | json_query
-------------
1 | []

Error handling examples

SQL

-- Handle type conversion errors
SELECT JSON_QUERY(
    '{"value": "not_a_number"}',
    '$.value'
    RETURNING numeric
    NULL ON ERROR
);

text

# | json_query
-------------
1 |

SQL

-- Raise error on invalid path
SELECT JSON_QUERY(
    '{"a": 1}',
    'invalid_path'
    ERROR ON ERROR
);

text

ERROR: syntax error at end of jsonpath input (SQLSTATE 42601)

Common use cases

Data transformation

SQL

-- Transform and validate JSON data
CREATE TABLE events (
    id SERIAL PRIMARY KEY,
    event_data JSONB
);

INSERT INTO events (event_data) VALUES
('{
    "type": "user_login",
    "timestamp": "2024-12-04T10:30:00Z",
    "details": {
        "user_id": "U123",
        "device": "mobile",
        "location": {"city": "London", "country": "UK"}
    }
}');

-- Extract specific fields with custom formatting
SELECT
    JSON_QUERY(event_data, '$.type' RETURNING TEXT OMIT QUOTES) as event_type,
    JSON_QUERY(event_data, '$.details.location' WITH WRAPPER) as location
FROM events;

text

# | event_type | location
-------------------------------------
1 | user_login | [{"city": "London", "country": "UK"}]

Performance considerations

Use appropriate options:
- Use RETURNING TEXT with OMIT QUOTES when JSON formatting is not required
- Choose CONDITIONAL WRAPPER over UNCONDITIONAL when possible
- Consider using DEFAULT expressions for better error recovery
Optimization tips:
- Create indexes on frequently queried JSON paths
- Use specific path expressions instead of wildcards when possible

Learn more

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Postgres JSON_QUERY() Function

Function signature

Understanding Wrappers and Quotes

Wrapper Behavior

Quote Behavior

Example usage

Working with single values

Working with multiple values

Using conditional wrapper

Quote handling

Using the PASSING clause

Handling empty results

Error handling examples

Common use cases

Data transformation

Performance considerations

Learn more

Related docs (JSON functions)