QUERY

Query
Name	QUERY
Namespace	System.Query
Internal Name	SystemObjects.QUERY
TypeString	UBIK.Kernel.MetaClass
RuntimeType	UBIK.Kernel.Query
Purpose	Configure queries
Version	2+

In UBIK, queries are used for fetching a list of ContentClasses from the database. Queries use data base mechanism for perfomant data access and will deliver a list of objects of a certain Metaclass. Queries can be used in different scenarios:

• data fetching (n records)
• finding a single or a set of recordset(s)
• used as definition of root nodes in a View

There are specific methods available for this type!

A Query is defined for a single MetaClass, where the MetaClass is defined in the property FILTEROBJECT. Once a query is evaluated it will deliver a list of objects of type ContentClasses (instances), filtered as defined by its QueryItems. The correspondence between Queries and its items is created and stored by a relationship SYSREL QUERY. Therefore a single QueryItem can be used several times for different Queries.

Objects can be loaded on demand from the server, as storing a huge amount of data permanently on the device would need too much resources.

A content query needs to be

• a QUERY instance classified as SYSCLS QUERY
• related either to other content objects (to show up somewhere in the view hierarchy) or placed as root object of a View
• described by a Query Scopes in the ACM

Further it is nessary to

• create a HowTo:Create_a_new_ViewItem for the query object itself
• Set filter object (FILTEROBJECT) similar as for other query
• Create a proper relation
• Create a query view item and set the instance as QUERY
• Create a relation view item and set the according default MetaClass and relation
• Create and relate a query context scope and set the instance as QUERY
• For the scope define the MetaProperties, which should be available as filter criteria on the client. Without appropriate query item, equality is used as filter operator (=)

1. Once the scan is finished, wait until the scanner is closed and an empty browser shows up;
2. Depending on the network connection and the UBIK^® sync mode, different ways of searching will be applied;
3. During the search, the list might show a searching text before any objects are found;
   
4. If any objects are found, they will be added to the list.
   

It is also possible to define a Database View and use this View for the evaluation of Queries (see VirtualContentClass).

• QUERYITEM