Why can't I use a CTE in my select statement?

问题

I have a Mule application running a DB query which runs perfectly well (albeit a little bit slow). It's details are:

Mule 3.7.2 EE
Anypoint Studio 5.4.1
jdk1.7.0_51
Using oracle ojdbc6 driver

Now when I create a database connection using the ojdbc6 driver, without the use of a Common Table Expression (CTE) the query runs fine (at 2.5 secs).

When I utilise my CTE, the query fails with the error:

org.mule.api.MessagingException: Query type must be one of '[SELECT, STORE_PROCEDURE_CALL]' but was 'DDL' (java.lang.IllegalArgumentException). Message payload is of type: NullPayload

Clearly at some point the Mule EE server thinks that I'm trying to execute DDL when I'm not.

The new query, using the CTE, works perfectly fine (at .250 sec) in SQL Developer, so I know that it's not my query.

Why can't I use the CTE (WITH) statement in Mule?

Is this a known issue? Am I doing something wrong?

Query (simplified) before CTE:

SELECT '1' AS COLUMN_ONE, 'X' AS COLUMN_X
FROM DUAL

Query (simplified) after CTE:

WITH TBL AS
(
    SELECT '1' AS COLUMN_ONE, 'X' AS COLUMN_X
    FROM DUAL
)
SELECT * FROM TBL

回答1:

As of 2016-04-27 the CTE statement is not supported by Mule.

I had to dig deep for this one.

I tweeted this question and tagged @MuleSoft and @MuleDev
- To which I got the reply:
  
  if you haven't already we'd also suggest posting this in the forums - http://forums.mulesoft.com
I then posted the issue on the Mulesoft Forums
- To no avail
I then logged a support ticket with Mulesoft (case number 00107313)
- To which I got the reply:
  
  WITH is not currently supported by Mule ESB. Enhancement request(SE-987) has been raised but not implemented yet.
  Engineering team work on JIRAs based on the priorities. If this JIRA is urgent to you, please provide the following information then I will escalate the JIRA for you

回答2:

For now you can resolve this writing an alternative select statement as in

Sql - alternative to WITH ... AS

It does not make sense and is very unlucky for Mule not to support CTE

来源：https://stackoverflow.com/questions/36142783/why-cant-i-use-a-cte-in-my-select-statement

标签

mule

common-table-expression

ojdbc