The error in XT Fiddle is:

Error: xtdb.IllegalArgumentException

Invalid SQL query: Parse error at line 6, column 12:
  NEST_MANY(SELECT o.xt$id AS order_id, o.value FROM orders o WHERE o.customer_id = c.xt$id) AS orders
           ^
Expected one of:
SUCCEEDS
OR
<regular identifier>
IN
IMMEDIATELY
YEAR
OVERLAPS
SECOND
IS
<delimited identifier>
>
=
<
CONTAINS
AS
NOT
AND
LIKE
DAY
/
.
>=
||
-
<=
,
+
MONTH
<>
*
HOUR
BETWEEN
??(
FROM
MINUTE
EQUALS
[
PRECEDES
LIKE_REGEX

Data:

{:errs ["Parse error at line 6, column 12:\n NEST_MANY(SELECT o.xt$id AS order_id, o.value FROM orders o WHERE o.customer_id = c.xt$id) AS orders\n ^\nExpected one of:\nSUCCEEDS\nOR\n<regular identifier>\nIN\nIMMEDIATELY\nYEAR\nOVERLAPS\nSECOND\nIS\n<delimited identifier>\n>\n=\n<\nCONTAINS\nAS\nNOT\nAND\nLIKE\nDAY\n/\n.\n>=\n||\n-\n<=\n,\n+\nMONTH\n<>\n*\nHOUR\nBETWEEN\n??(\nFROM\nMINUTE\nEQUALS\n[\nPRECEDES\nLIKE_REGEX\n"], :xtdb.error/error-key "xtdb.sql/parse-error"}

Hey @U073TJ6238Q thanks for taking a look and reporting the issue! 🙂 unfortunately the published snapshot jar that the Fiddle server depends on is waiting on a refresh... sorry about the confusion. We should have it upgraded to the latest version sometime next week. In the meantime though you should at least be able to clone and build XT2 as a local artefact to try it out

this is some alternative SQL instead of NEST_MANY (https://fiddle.xtdb.com/?version=2.0.0-SNAPSHOT&type=sql&txs=W3sic3lzdGVtLXRpbWUiOm51bGwsInR4cyI6IklOU0VSVCBJTlRPIGN1c3RvbWVycyAoeHQkaWQsIG5hbWUpIFZBTFVFUyAoMSwgJ0ZyZWQnKTtcbklOU0VSVCBJTlRPIG9yZGVycyAoeHQkaWQsIGN1c3RvbWVyX2lkLCB2YWx1ZSkgVkFMVUVTICgxLCAxLCA4Ljk5KTtcbklOU0VSVCBJTlRPIG9yZGVycyAoeHQkaWQsIGN1c3RvbWVyX2lkLCB2YWx1ZSkgVkFMVUVTICgyLCAxLCAyNi4yMCk7XG4ifV0%3D&query=U0VMRUNUIGMueHQkaWQgQVMgY3VzdG9tZXJfaWQsIGMubmFtZSwKICAgICAgKFNFTEVDVCBBUlJBWV9BR0cocmVsLmNvbCkgQVMgb3JkZXJzCiAgICAgICBGUk9NIChTRUxFQ1QgeydvcmRlcl9pZCc6IG8ueHQkaWQsCiAgICAgICAgICAgICAgICAgICAgICd2YWx1ZSc6IG8udmFsdWV9IEFTIGNvbAogICAgICAgICAgICAgRlJPTSBvcmRlcnMgbwogICAgICAgICAgICAgV0hFUkUgby5jdXN0b21lcl9pZCA9IGMueHQkaWQpIEFTIHJlbCkKRlJPTSBjdXN0b21lcnMgYwoKICAK):

SELECT c.xt$id AS customer_id, c.name,
      (SELECT ARRAY_AGG(rel.col) AS orders
       FROM (SELECT {'order_id': o.xt$id,
                     'value': o.value} AS col
             FROM orders o
             WHERE o.customer_id = c.xt$id) AS rel)
FROM customers c