Allowing ()'s to group UNIONs in the grammar

[Blair Zajac]

We have a query on a snowflake schema and want to generate a list of PKs on the 
master parent table from UNION, INTERSECT and EXCEPT on child tables.

In trying to write a clearer query I added ()'s around the sub-queries that are 
being UNIONed together, but Derby doesn't accept it.  For example, this query works:

SELECT
  parent.pk_parent
FROM
  parent
WHERE
  EXISTS (
    SELECT
      1
    FROM (
      SELECT
        child1.pk_parent
      FROM
        child1
      WHERE
        child1.name = 'foobar'
      UNION
      SELECT
        child2.pk_parent
      FROM
        child2
      WHERE
        child2.zipcode = '12345'
    )
  AS results WHERE results.pk_parent = parent.pk_parent);

but this one doesn't:

SELECT
  parent.pk_parent
FROM
  parent
WHERE
  EXISTS (
    SELECT
      1
    FROM (
      (
        SELECT
          child1.pk_parent
        FROM
          child1
        WHERE
          child1.name = 'foobar'
      ) UNION (
        SELECT
          child2.pk_parent
        FROM
          child2
        WHERE
          child2.zipcode = '12345'
      )
    )
  AS results WHERE results.pk_parent = parent.pk_parent);

Either form works written this way, but when all the whitespace and newlines are 
removed and appearing in my Java server's log it's easier to read it with ()'s.

Is this worth opening an enhancement request for?

Regards,
Blair

Here's the DML to create the tables:



CREATE TABLE child1 (pk_child1 INT PRIMARY KEY,
                     pk_parent INT NOT NULL,
                     name VARCHAR(1024));
ALTER TABLE
  child1
ADD CONSTRAINT
  fk_child1_pk_parent
FOREIGN KEY
  (pk_parent)
REFERENCES
  parent(pk_parent);

CREATE TABLE child2 (pk_child2 INT PRIMARY KEY,
                     pk_parent INT NOT NULL,
                     zipcode VARCHAR(1024));
ALTER TABLE
  child2
ADD CONSTRAINT
  fk_child2_pk_parent
FOREIGN KEY
  (pk_parent)
REFERENCES
  parent(pk_parent);