Using Caché Objects - InterSystems Documentation

Objects and SQL
The identity column has the name “ID” , unless the object has a property named “ID” ; in
that case, the identity column has “ID1” as its name. (If there are ID and ID1 properties, the
identity column has “ID2” as its name, and so on.)
13.2.1.1 ID Column Constraints
Though the ID appears as a column in the projection, there is no need to create an index based
on it, as it is already the IDKEY for the table; further, it has no equivalent property, so an index
created specifically for a class' SQL projection is not meaningful for the class itself.
Additionally, you cannot perform UPDATE or INSERT operations on it, since Caché generates
ID values automatically. For instance, here is the syntax to add a new instance of a
class through its projection (where the ID column is created from the class OID):
INSERT INTO PERSON (FNAME, LNAME)VALUES (:fname, :lname)
and not:
INSERT INTO PERSON (ID, FNAME, LNAME)VALUES (:id, :fname, :lname)
Because the ID field is handled automatically, you do not need to refer to it explicitly.
13.2.2 Properties
When projected, most properties appear in a relational table as columns (fields), where the
column takes its name from the property; the exception is arrays, which are projected as child
tables by default.
All a class' properties are projected, aside from the following exceptions:
• Transient properties
• Calculated properties
• Private properties
• Multidimensional properties
For information on managing the projection of transient or calculated properties, see Transient
and Calculated Properties.
116 Using Caché Objects