Column Name Conventions

Column Name Conventions

Column names follow identifier conventions, with the same naming restrictions as table names. Avoid beginning column names beginning with a % character, though column names beginning with %z or %Z are permitted. A column name should not exceed 128 characters. By default, column names are simple identifiers. They are not case-sensitive. Attempting to create a column name that differs only in letter case from another column in the same table generates an SQLCODE -306 error.

InterSystems IRIS uses the column name to generate a corresponding class property name. A property name contains only alphanumeric characters (letters and numbers) and is a maximum of 96 characters in length. To generate this property name, InterSystems IRIS first strips punctuation characters from the column name, and then generates a unique identifier of 96 or fewer characters. InterSystems IRIS substitutes an integer, beginning with 0, for the final character of a column name when this is needed to create a unique property name.

This example shows how InterSystems IRIS handles column names that differ only in punctuation. The corresponding class properties for these columns are named PatNum, PatNu0, and PatNu1:

CREATE TABLE MyPatients (
    _PatNum VARCHAR(16),
    %Pat@Num INTEGER,
    Pat_Num VARCHAR(30),
    CONSTRAINT Patient_PK PRIMARY KEY (_PatNum))

The column name, as specified in CREATE TABLE, is shown in the class property as the SqlFieldName keyword value.

During a dynamic SELECT operation, InterSystems IRIS might generate property name aliases to facilitate common letter case variants. For example, given the column name Home_Street, InterSystems IRIS might assign the property name aliases home_street, HOME_STREET, and HomeStreet. InterSystems IRIS does not assign an alias if that name would conflict with the name of another field name, or with an alias assigned to another field name.