表被指定两次，既作为 'UPDATE' 的目标，也作为单独的数据源

Question

I use spring-jpa with hibernate implementation. I use mariadb and I try to do an update subquery

My object structure

@Entity
public class Room {
  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long roomId;

  @ManyToOne  
  @JoinColumn(name = "appartment_id")
  private Appartment appartment;
}

@Entity
public class Appartment {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long appartmentId;

  @OneToMany
  @JoinColumn(name="appartment_id")
  private Set<Room> roomList;
}

update Room r1
set r1.available = :availability
where r1.roomId in
( select r2.roomId from Room r2 JOIN r2.appartment a1 WHERE a1.appartmentId = :appartmentId )

I get this error

java.sql.SQLException: Table 'room' is specified twice, both as a target for 'UPDATE' and as a separate source for data

Answer 1

This is a restriction in MySQL:-

http://dev.mysql.com/doc/refman/5.7/en/update.html

You cannot update a table and select from the same table in a subquery.

There is a fudge you can do sometimes do to hide the sub query in aa further level of sub query that might work. Something like this (not tested):-

UPDATE Room r1
SET r1.available = :availability
WHERE r1.roomId IN
    SELECT roomId
    FROM
    ( 
        SELECT r2.roomId 
        FROM Room r2 
        JOIN r2.appartment a1 
        WHERE a1.appartmentId = :appartmentId 
    )

Note that your query possibly has an error. In the sub query you are joining the table Room aliased as r2 to a table called appartment on a database called r2. Also your sub query does a JOIN without a join condition.

However you can quite possibly just do the join in the UPDATE statement without the need for a sub query:-

UPDATE Room 
INNER JOIN r2.appartment a1
ON Room.roomId = a1.roomId
SET r1.available = :availability
WHERE a1.appartmentId = :appartmentId 

Answer 2

A solution will be to select roomIds seperatly and pass them as a parameter.

Select id list

List<Long> roomIdList = entityManager.createQuery(
                    """SELECT r2.roomId 
                    FROM Room r2 
                    JOIN r2.appartment a1 
                    WHERE a1.appartmentId = :appartmentId""", Long.class)
                    .setParameter("appartmentId", appartmentId)
                    .getResultList();

Pass it as a parameter

int updated = entityManager.createQuery(
                    """UPDATE Room r1
                    SET r1.available = :availability
                    WHERE r1.roomId IN :roomIds""")
                    .setParameter("availability", availability)
                    .setParameter("roomIds", roomIdList)
                    .executeUpdate();