Using UNION in a subquery leads to a syntax error in Sqlite #329
Description
Hi, I'm attempting to use a UNION in a subquery, and that is leading to a syntax error when executing the query against a Sqlite backend. Based on attempting to understand the issue, I believe it is a bug in the ORM similar to this other project.
Apparently MySQL and Postgres tolerate (SELECT ...) UNION (SELECT ...), but this is not correct syntax. There should be no parenthesis around the individual selects around a union. It should be SELECT ... UNION SELECT ....
The code I'm running is,
val files = this.session
.from( Objects )
.select( Objects.object_id )
.where { Objects.object_type eq TYPE_FILE }
val albums = this.session
.from( Objects )
.select( Objects.object_id )
.where { Objects.object_type eq TYPE_ALBUM }
val all_children = this.session
.from( Relations )
.select( Relations.child_id )
.where { Relations.parent_id inList albums }
val free_files = files.where { Objects.object_id notInList all_children }
val select_ids = free_files.union( albums )
val query = this.session
.from( Objects )
.select()
.where { Objects.object_id inList select_ids }
.orderBy( randOrder() )
Which yeilds the following query:
SELECT *
FROM objects
WHERE objects.object_id IN (
(
SELECT objects.object_id AS objects_object_id
FROM objects WHERE objects.object_id NOT IN (
SELECT relations.child_id AS relations_child_id
FROM relations
WHERE relations.parent_id IN (
SELECT objects.object_id AS objects_object_id
FROM objects WHERE objects.object_type = ?
)
)
)
UNION (
SELECT objects.object_id AS objects_object_id
FROM objects
WHERE objects.object_type = ?
)
)
ORDER BY RANDOM();
Both when executed via the code, and directly into sqlite3 this query fails with,
Error: near "UNION": syntax error
Manually removing the extra parenthesis such that the query reads as follows, works.
SELECT *
FROM objects
WHERE objects.object_id IN (
SELECT objects.object_id AS objects_object_id
FROM objects WHERE objects.object_id NOT IN (
SELECT relations.child_id AS relations_child_id
FROM relations
WHERE relations.parent_id IN (
SELECT objects.object_id AS objects_object_id
FROM objects WHERE objects.object_type = ?
)
)
UNION
SELECT objects.object_id AS objects_object_id
FROM objects
WHERE objects.object_type = ?
)
ORDER BY RANDOM();