Relationship attributes

This relationship attribute is intended only for dealing with exceptional cases that are not typically good design.

By default, Foreign Key Mandatory = Yes if all the foreign key columns in the relationship have Mandatory = Yes. Otherwise, by default, Foreign Key Mandatory = No.

As a rule, you should not tamper with this default.

If Foreign Key Mandatory = Yes, in each child record, each Child Column of the relationship must have a value other than NULL. This is often expressed by saying that "the relationship is mandatory". While it's important to decide, for each relationship separately, if you want it to be mandatory or not, you should generally express this decision by setting Mandatory = Yes or Mandatory = No at Column level (= when defining the foreign key), not by setting Foreign Key Mandatory.

When you are in the Relationships window, the Foreign Key Mandatory checkbox allows you to see at a glance whether the relationship is mandatory or not, but it is not generally the place where you should express this.

Only if Foreign Key Mandatory = No can you use the Check Partial Foreign Key checkbox to express how NULL values in multi-column foreign keys must be treated.

If all the foreign key columns in the relationship have Mandatory = Yes, you cannot change the default Foreign Key Mandatory = Yes.

This relationship attribute is intended only for dealing with exceptional cases that are not typically good design.

By default, Check Partial Foreign Key = Yes.

As a rule, you should not tamper with this default.

In relationships where the key spans more than one column, you can specify that partial foreign keys are not to be checked, where "to check" means to validate that the value entered in the foreign key field is an existing value in the corresponding parent column. Partial foreign keys occur when one or more foreign key columns have the NULL value. An exception to this rule is when the parent column on which you set the NULL value is not mandatory (allows NULL values). In this case the NULL value should be checked since it is an allowed value.

If you clear the Check Partial Foreign Key checkbox in the Relationships info window, in partial foreign keys none of the foreign key column values are checked. This is not generally recommended because, as a result, foreign key column values that do not exist in the corresponding primary key column are allowed into the database if one of the other foreign key columns has the NULL value.

Only consider clearing the Check Partial Foreign Key checkbox in special cases such as overlapping foreign key situations, e.g. columns A and B form one foreign key, and columns A and C another. This allows the user to enter child records with values for A and B but not C. These records are checked with regard to the relationship on columns A-B, while the relationship on columns A-C is not checked until a value for column C is provided.

You can only clear this checkbox if you clear the Foreign Key Mandatory checkbox as well.

If Lock Foreign Key on Check = Yes (the default), the parent record is locked whilst changes are made to child records.

In some situations this behavior may be undesirable. For example, if there are few parent records but each have many child records, users editing unrelated child records could lock each other out. If the parent table is not subject to many changes, it may be better not to lock the parent. In this case, set Lock Foreign Key = No.

Set this attribute to restrict updatability of foreign key values in the relationship.

By default, Foreign Key Updatable = Yes.

As a rule, you should not tamper with this default.

You can restrict the updatability of a column at Column level by setting the Updatable attribute. Cases are very few where you want to restrict updatability specifically at the Relationship level and not at the Column level. But even at the Column level, restricting updatability is often unnecessary and complicates data management operations.

If you set Child Must Exist = Yes, for each parent record in the relationship, there must be at least 1 child record that refers to that parent record.

By default, Child Must Exist = No.

Setting Child Must Exist = Yes is equivalent to setting Minimum Children = 1.

If you set Minimum Children to an integer value, for each parent record in the relationship, there must be at least this number of child records referring to that parent record.

By default, Minimum Children is empty (NULL).

Setting Minimum Children = 1 is equivalent to setting Child Must Exist = Yes.

If you set Maximum Children to an integer value, for each parent record in the relationship, there may be no more than this number of child records referring to that parent record.

By default, Maximum Children is empty (NULL).

This attribute controls how USoft Definer generates default GUI behavior for the relationship for users who want to select a foreign key value from the set of available parent values ("lookup" behaviour).

This attribute determines what happens to child records when the parent record is deleted.

This attribute determines what happens to child records when the primary key value of the parent record is updated to a different value.

This attribute can be used to specify the nature of the relationship between the parent and the child.

Setting this attribute to "Composition" may cause child records to be automatically deleted during parent-child import operations.