CODEWITHSUNDEEP
javajpamany-to-manyjpqlnamed-query
Lex Bauer
Lex Bauer

Reputation: 15

JPQL query that returns entities involving a many to many relationship

I need a JPQL query that returns:

I tried something like:

SELECT t
FROM Tweet t
WHERE t.author.id = :userId
OR t.author.id IN (
    SELECT u.followedUsers
    FROM User u
    WHERE u.id = :userId
)

Only to find out that the subquery has wrong syntax. Also I cannot call the relation table User_User, like I would in SQL, because JPA doens't recognize it

User

@Entity
public class User {

    @Id
    @GeneratedValue
    private long id

    @ManyToMany(mappedBy = "followedUsers")
    private Set<User> followers;

    @ManyToMany
    private Set<User> followedUsers;

}

Tweet

@Entity
public class Tweet {

    @Id
    @GeneratedValue
    private long id;

    @ManyToOne
    private User author;

}

Upvotes: 1

Views: 1015

Answers (2)

Ammar Akouri
Ammar Akouri

Reputation: 526

given this query

OR t.author.id IN (
            SELECT u.followedUsers
            FROM User u
            WHERE u.id = :userId
        )

you are trying to find an Integer (t.author.id) in a list of User objects ! I think this should work :

 SELECT t
    FROM Tweet t
    WHERE t.author.id = :userId
    OR t.author MEMBER OF (
        SELECT u.followedUsers
        FROM User u
        WHERE u.id = :userId
    )

Edit

... MEMBER OF (subquery)... isn't allowed, but merging the subquery into its parent resolves this.

SELECT DISTINCT(t)
FROM Tweet t, User u
WHERE t.author.id = :userId
OR (t.author MEMBER OF u.followedUsers AND u.id = :userId)

Upvotes: 0

Dherik
Dherik

Reputation: 19060

I have the habit of making JPQL queries more similar to SQL queries. So, my suggestion:

SELECT t FROM Tweet t
JOIN t.author a
WHERE a.id = :idUser
OR a.id IN (SELECT followedUser.id 
    FROM User u
    JOIN u.followedUsers followedUser
    WHERE u.id = :idUser)

Upvotes: 1

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