export-to-parquet-composite-queries.md
The query can contain only a single outer SELECT statement. For example, you cannot use UNION:
=> EXPORT TO PARQUET(directory = '/mnt/shared_nfs/accounts/rm')
OVER(PARTITION BY hash)
AS
SELECT 1 as account_id, '{}' as json, 0 hash
UNION ALL
SELECT 2 as account_id, '{}' as json, 1 hash;
ERROR 8975: Only a single outer SELECT statement is supported
HINT: Please use a subquery for multiple outer SELECT statements
Instead, rewrite the query to use a subquery:
=> EXPORT TO PARQUET(directory = '/mnt/shared_nfs/accounts/rm')
OVER(PARTITION BY hash)
AS
SELECT
account_id,
json
FROM
(
SELECT 1 as account_id, '{}' as json, 0 hash
UNION ALL
SELECT 2 as account_id, '{}' as json, 1 hash
) a;
Rows Exported
---------------
2
(1 row)
To use composite statements such as UNION, INTERSECT, and EXCEPT, rewrite them as subqueries.