Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I've looked this up. It looks as though the joins are done in the object layer. </p> <p>Extrapolated from <a href="http://exploring.liftweb.net/master/index-8.html" rel="nofollow">http://exploring.liftweb.net/master/index-8.html</a> to your case: </p> <pre><code>// Accessing foreign objects class Employee extends LongKeyedMapper[Employee] with IdPK { ... object department extends MappedLongForeignKey(this, Department) def departmentName = Text("My department is " + (department.obj.map(_.name.is) openOr "Unknown")) } class Department ... { ... def entries = Employee.findAll(By(Employee.department, this.id)) } </code></pre> <p>If you want to do many-to-many mappings you’ll need to provide your own<br> “join” class with foreign keys to both of your mapped entities. </p> <pre><code>// DepartmentId Entity class DepartmentId extends LongKeyedMapper[DepartmentId] with IdPK { def getSingleton = DepartmentId object name extends MappedString(this,100) } object DepartmentId extends DepartmentId with LongKeyedMetaMapper[DepartmentId] { override def fieldOrder = List(name) } </code></pre> <p>Next, we define our join entity, as shown below.<br> It’s a LongKeyedMapper just like the rest of the entities,<br> but it only contains foreign key fields to the other entities. </p> <pre><code>// Join Entity class DepartmentIdTag extends LongKeyedMapper[DepartmentIdTag] with IdPK { def getSingleton = DepartmentIdTag object departmentid extends MappedLongForeignKey(this,DepartmentId) object Employee extends MappedLongForeignKey(this,Employee) } object DepartmentIdTag extends DepartmentIdTag with LongKeyedMetaMapper[DepartmentIdTag] { def join (departmentid : DepartmentId, tx : Employee) = this.create.departmentid(departmentid).Employee(tx).save } </code></pre> <p>To use the join entity, you’ll need to create a new instance and set the<br> appropriate foreign keys to point to the associated instances. As you can see,<br> we’ve defined a convenience method on our Expense meta object to do just that.<br> To make the many-to-many accessible as a field on our entities, we can use the<br> HasManyThrough trait, as shown below </p> <pre><code>// HasManyThrough for Many-to-Many Relationships class Employee ... { object departmentids extends HasManyThrough(this, DepartmentId, DepartmentIdTag, DepartmentIdTag.departmentid, DepartmentIdTag.Employee) } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POComplex SQL Query With Join In Liftweb
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POComplex SQL Query With Join In Liftweb
      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. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThanks a lot for your very complete answer, reading the source you provided I found this chapter which could also help: http://exploring.liftweb.net/master/index-8.html#sub:SQL-based-queries I will do some test and post an answer if it works to. However your answer is very interesting and will certainly help a lot of SO users.
      singulars
      1. PO
      1. USChristopher Chiche
 

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