Obtención de la longitud y el tamaño de las matrices JSON

Ejemplo: json_array_length

Para obtener la longitud de una matriz con codificación JSON, use la función json_array_length.

WITH dataset AS (
  SELECT * FROM (VALUES
    (JSON '{"name":
            "Bob Smith",
            "org":
            "legal",
            "projects": [{"name":"project1", "completed":false}]}'),
    (JSON '{"name": "Susan Smith",
            "org": "engineering",
            "projects": [{"name":"project2", "completed":true},
                         {"name":"project3", "completed":true}]}'),
    (JSON '{"name": "Jane Smith",
             "org": "finance",
             "projects": [{"name":"project2", "completed":true}]}')
  ) AS t (users)
)
SELECT
  json_extract_scalar(users, '$.name') as name,
  json_array_length(json_extract(users, '$.projects')) as count
FROM dataset
ORDER BY count DESC

Esta consulta devuelve este resultado:

+---------------------+
| name        | count |
+---------------------+
| Susan Smith | 2     |
+---------------------+
| Bob Smith   | 1     |
+---------------------+
| Jane Smith  | 1     |
+---------------------+

Ejemplo: json_size

Para obtener el tamaño de una matriz u objeto con codificación JSON, utilice la función json_size y especifique la columna que contiene la cadena JSON y la expresión JSONPath de la matriz u objeto.

WITH dataset AS (
  SELECT * FROM (VALUES
    (JSON '{"name": "Bob Smith", "org": "legal", "projects": [{"name":"project1", "completed":false}]}'),
    (JSON '{"name": "Susan Smith", "org": "engineering", "projects": [{"name":"project2", "completed":true},{"name":"project3", "completed":true}]}'),
    (JSON '{"name": "Jane Smith", "org": "finance", "projects": [{"name":"project2", "completed":true}]}')
  ) AS t (users)
)
SELECT
  json_extract_scalar(users, '$.name') as name,
  json_size(users, '$.projects') as count
FROM dataset
ORDER BY count DESC

Esta consulta devuelve este resultado:

+---------------------+
| name        | count |
+---------------------+
| Susan Smith | 2     |
+---------------------+
| Bob Smith   | 1     |
+---------------------+
| Jane Smith  | 1     |
+---------------------+