Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>When you are working with JPA, you should think Object and relations between Objects and you should map your Object model, not <code>ids</code>, to your relational model (it is possible to map a <code>List</code> of basic values with <a href="http://en.wikibooks.org/wiki/Java_Persistence/ElementCollection" rel="nofollow noreferrer"><code>@ElementCollection</code></a> in JPA 2.0 though but what I said just before still applies).</p> <p>Here, (assuming this really is a <strong>one-to-many</strong> relation between <code>Message</code> and <code>GroupAssoc</code> and not a <strong>many-to-many</strong> relation between <code>Message</code> and <code>Group</code> entities) you should have something like this:</p> <pre><code>@Entity @Table(name = "MESSAGE") public class Message implements Serializable { @Id @Column(name = "MESSAGE_ID") @GeneratedValue(strategy = GenerationType.IDENTITY) private Long messageId; @OneToMany(fetch=FetchType.LAZY, cascade=CascadeType.PERSIST) private List&lt;GroupAssoc&gt; groupAssocs = new ArrayList&lt;GroupAssoc&gt;(); public Long getMessageId() { return messageId; } public void setMessageId(Long messageId) { this.messageId = messageId; } public List&lt;GroupAssoc&gt; getGroupAssocs() { return groupAssocs; } public void setGroupAssocs(List&lt;GroupAssoc&gt; groupAssocs) { this.groupAssocs = groupAssocs; } // equals() and hashCode() } </code></pre> <p>And another entity for <code>GroupAssoc</code>.</p> <p>PS: Your DDL really looks like a (M:N) relation between <code>MESSAGE</code> and <code>GROUP</code> (or I don't understand the PK constraint of <code>GROUP_ASSOC</code>) but you didn't show any FK constraint on <code>GROUP_ID</code> so I'm not 100% sure. But if that's the case, then you should use an <code>@ManyToMany</code> instead of <code>@OneToMany</code>.</p>
    singulars
    1. This table or related slice is empty.
    1. POThe type of field isn't supported by declared persistence strategy "OneToMany"
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USPascal Thivent
    1. USPascal Thivent
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POThe type of field isn't supported by declared persistence strategy "OneToMany"
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThank you very much for your help. I should have mentioned that our application needs to display groupIds (in the UI) and that list of groupId's is what we ultimately need to query for by message. I think it is an M:N relationship because two massages may share the same groupIds.
      singulars
      1. PO
      1. USLightbeard
    2. COMy DDL is my best guess as to how to efficiently model this list of integers so there may be a problem with it (I'm a UI developer not a DBA). It seems cumbersome to create a separate `GroupAssoc` pojo especially if we have to create a third identity class (since it has a composite primary key) just to query for a list of groupIds for a given message.
      singulars
      1. PO
      1. USLightbeard
    3. CO@Robert You wouldn't have to create a third entity, JPA abstract the implementation at the database level. So you would get a List of `GroupAssoc` and iterate on the list to get each id.
      singulars
      1. PO
      1. USPascal Thivent
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload