Available in versions: Dev (3.21)

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NULL ON NULL

Supported by ✅ Open Source Edition   ✅ Express Edition   ✅ Professional Edition   ✅ Enterprise Edition

The JSON_ARRAY from query function has a NULL ON NULL clause to indicate that NULL values should be included in the output JSON array:

SELECT json_array(
  SELECT language.description FROM language
  NULL ON NULL
)
FROM language
create.select(jsonObject(
          select(LANGUAGE.CD).from(LANGUAGE))
          .nullOnNull())
      .from(LANGUAGE)
      .fetch();

The result would look like this:

+------------------+
| json_array       |
+------------------+
| ["English",null] |
+------------------+

Dialect support

This example using jOOQ:

jsonArray(select(LANGUAGE.DESCRIPTION).from(LANGUAGE)).nullOnNull()

Translates to the following dialect specific expressions:

Aurora Postgres, Postgres, YugabyteDB

coalesce(
  json_array(
    SELECT LANGUAGE.DESCRIPTION
    FROM LANGUAGE
    RETURNING json
  ),
  cast('[]' AS json)
)

BigQuery, ClickHouse, DB2, H2, Oracle, Snowflake

json_array(
  SELECT LANGUAGE.DESCRIPTION
  FROM LANGUAGE
)

CockroachDB

coalesce(
  (
    SELECT json_agg(a)
    FROM (
      SELECT LANGUAGE.DESCRIPTION
      FROM LANGUAGE
    ) t (a)
  ),
  cast('[]' AS json)
)

DuckDB

coalesce(
  (
    SELECT to_json(array_agg(a))
    FROM (
      SELECT LANGUAGE.DESCRIPTION
      FROM LANGUAGE
    ) t (a)
  ),
  JSON '[]'
)

MariaDB

ifnull(
  (
    SELECT json_merge_preserve(
      '[]',
      concat(
        '[',
        group_concat(json_quote(a) SEPARATOR ','),
        ']'
      )
    )
    FROM (
      SELECT LANGUAGE.DESCRIPTION a
      FROM LANGUAGE
    ) t
  ),
  json_extract('[]', '$')
)

MySQL

ifnull(
  (
    SELECT json_merge_preserve(
      '[]',
      concat(
        '[',
        group_concat(json_quote(a) SEPARATOR ','),
        ']'
      )
    )
    FROM (
      SELECT LANGUAGE.DESCRIPTION
      FROM LANGUAGE
    ) t (a)
  ),
  cast('[]' AS json)
)

Spanner

(
  SELECT to_json(
    coalesce(
      array_agg(a), cast(ARRAY[] AS array<string>)
    )
  )
  FROM (
    SELECT LANGUAGE.DESCRIPTION a
    FROM LANGUAGE
  ) t
)

SQLite

(
  SELECT json_group_array(a)
  FROM (
    SELECT LANGUAGE.DESCRIPTION a
    FROM LANGUAGE
  ) t
)

SQLServer

coalesce(
  (
    SELECT json_query(('[' + string_agg(cast(
      ('"' + replace(a, '"', '\"') + '"')
      AS varchar(max)
    ), ',') + ']'))
    FROM (
      SELECT LANGUAGE.DESCRIPTION
      FROM LANGUAGE
    ) t (a)
  ),
  '[]'
)

Trino

coalesce(
  (
    SELECT cast(array_agg(a) AS json)
    FROM (
      SELECT LANGUAGE.DESCRIPTION
      FROM LANGUAGE
    ) t (a)
  ),
  json_parse('[]')
)

ASE, Access, Aurora MySQL, Databricks, Exasol, Firebird, HSQLDB, Hana, Informix, MemSQL, Redshift, SQLDataWarehouse, Sybase, Teradata, Vertica

/* UNSUPPORTED */
Generated with jOOQ 3.21. Support in older jOOQ versions may differ. Translate your own SQL on our website

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