Using Caché Objects - InterSystems Documentation

Objects and SQL
Note:
There is no Siblings column in the parent table.
For the column(s) containing the array members, the number and contents of the column(s)
depend on the kind of array:
• The projection of an array of data type properties is a single column of data.
• The projection of an array of reference properties is a single column of object references.
• The projection of an array of embedded objects is as multiple columns in the child table.
The structure of these columns is as is described in the section Embedded Object Properties.
Together, the ID of each instance and the identifier of each array member comprise a unique
index for the child table. Also, if a parent instance has no array associated with it, it has no
associated entries in the child table.
13.2.2.7 List Properties
A list property is projected as a string in $LIST format, which means that all the elements
within the collection are concatenated and projected as a single string. For example, suppose
the Person class has a Cars list property, where Cars is a list of strings that are license plate
numbers. This property appears as a single column called Cars and might appear in the Person
projection as follows (looking at a partial view of the table):
Sample Projection of a List Property
ID
1
2
3
Cars
324WLI,395BCE
253COM
512SEL,710LRR,526SJL
The list field contains a string constructed by concatenating the individual elements of the
list:
New cars
&sql(SELECT Cars INTO :cars
FROM Person
WHERE ID = :id)
Given an id value of 1, cars has a value equivalent to a list based on the “324WLI” and “
395BCE” strings.
120 Using Caché Objects