Relation
Overview
A relation between two database tables refers to how data in one table is related to data in another table, it is an object from the datalayer that provides the link from one datasource to another, based on one or more matches between the dataproviders in the datasource and an operator. These relationships are established using keys, typically primary keys and foreign keys.
Property Summary
Properties Details
allowCreationRelatedRecords
This option is enabled by default and it specifies that records can be created within a related foundset. Moreover, when records are created in a related foundset, the key columns in the new record may be automatically filled with the corresponding values from the source record.
Example: Assume a relation, customers_to_orders defined by a single key expression, customers.customerid = orders.customerid
Key columns will be auto-filled for expressions using the following operators:* =
#=
^||=
If this option is disabled, then records cannot be created in a related foundset. If attempted a ServoyException is raised with the error code, NO_RELATED_CREATE_ACCESS.
Flag that tells if related records can be created through this relation.
The default value of this flag is "false".
Type Boolean
Sample
allowParentDeleteWhenHavingRelatedRecords
This option is enabled by default. When disabled, it will prevent the deleting of a record from the source table if the related foundset contains one or more records. If the delete fails, a ServoyException is raised with the error code, NO_PARENT_DELETE_WITH_RELATED_RECORDS.
Example: Assume the relation customers_to_orders has disabled this option. An attempt to delete a customer record will fail, if that customer has one or more orders.
Flag that tells if the parent record can be deleted while it has related records.
The default value of this flag is "true".
Type Boolean
Sample
comment
Additional information, such as programmer notes about the relation's purpose.
Type String
Sample
deleteRelatedRecords
This option specifies that records in a related foundset can be deleted. Moreover, it also enforces a cascading delete, such that when a source record is deleted, all records in the related foundset will also be deleted, eliminating the possibility of orphaned records.
Example: Assume the relation customers_to_orders has enabled this option. The deleting of the customer record will cause all related order records to be deleted.
Flag that tells if related records should be deleted or not when a parent record is deleted.
The default value of this flag is "false".
Type Boolean
Sample
deprecated
A relation can be deprecated, and a description has to be provided to hint users about what the alternative is.
Type String the deprecate info for this element or null if it is not deprecated
Sample
encapsulation
A relation has encapsulation property, similar to the form encapsulation property. The following can be used/checked:
Public – accessible from everywhere
Hide in Scripting; Module Scope – code completion is disabled for the relation, and it is accessible only from the module that it was created in
Module Scope – accessible from the module it was created in
For non-public encapsulation, if the relation is accessed from somewhere else, you get a build marker in Problems View, but it will still function properly.
Type Number the encapsulation mode/level of the persist.
Sample
foreignDataSource
Qualified name of the foreign data source. Contains both the name of the foreign server and the name of the foreign table. It is selectable from all available tables and has this format: "server-name.table-name".
Can be any database table or view from any named server connection and is not limited to the same database as the destination table.
At runtime, a related foundset will contain records from the destination table.
The destination table can exist in a separate database from the source table. This is a powerful feature, but it is worth noting that a related foundset, who's relation is defined across two databases will not be available when the source foundset is in find mode. This is because a related find requires a SQL JOIN, which cannot be issued across databases for all vendors.
Type String
Sample
initialSort
Foundsets, including related foundsets, have a sort property. By default, any foundset is sorted by the primary key(s) of the table upon which it is based. Relations have an Initial Sort property, which overrides the default sort, such that any related foundset is initialized to use the sorting definition defined by the relation object. For more information see foundset sorting. A String which specified a set of sort options for the initial sorting of data retrieved through this relation. Has the form "column_name asc, another_column_name desc, ...".
Type String
Sample
joinType
The join type that is performed between the primary table and the foreign table. Can be "inner join" or "left outer join".
Type Number
Sample
A relation can specify one of two SQL Join Types. A SQL join used when a find or a sort is performed using related criteria and thus, the join type will affect behavior in these situations.
Inner Join
SQL Inner Join does not return any rows for parent records which have no related records. Therefore, if a sort or a find is performed when a related data provider is used for criterion, the related foundset may have records omitted due parents with no child records.
Left Outer Join
SQL Left Outer Join will return always return a row for the parent record even if there are no related records. Therefore, if a sort or a find is performed when a related data provider is used for a criterion, the related foundset will include all matching records, regardless of the presence of related records.
Example: Assume that the user chooses to sort a customer list containing 50 records. The sort is based on the account manager's last name, which is in the employees table. However, 3 of the customers don't have an employee listed to manage the account.
name
The name of the relation.
Type String
Sample
primaryDataSource
Qualified name of the primary data source. Contains both the name of the primary server and the name of the primary table. Can be any database table or view from any named server connection.
At runtime, a related foundset will exist in the context of a single record from the source table. For example, the relation customer_to_orders
, will become available in the context of any record in a foundset which is based on the customers
table.
Type String
Sample
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