38) GEN Attributes rules, modeling considerations
· Although not a requirement, each entity type should have
at least one attribute for view reference and Transformation.
· Each attribute is implemented as a field in a record
during database Transformation. When the
database is implemented as a relational database, each attribute is implemented
as a column in at least one table. It
can be implemented in multiple tables because of usage as a foreign key, and
when denormalization occurs.
· Fixed-length text (CHAR) attributes are limited to 255
characters. The length specification
excludes the decimal point, which is implied.
Varying-length text (VARCHAR) attributes can be longer than 255
characters, but only 255 characters can be displayed in a single field on a
screen. Up to 4096 characters can be
displayed in a window, but only if they are displayed in a multi-line entry
field.
· The maximum length of variable length text (VARCHAR)
strings varies by DBMS and GEN, COOLGEN release. Specific DBMSs support different maximum
lengths of VARCHAR (variable character string) datatypes. These string datatypes include maximum number
of columns in an index, maximum length of a compound key, maximum number of
columns in a table, and the maximum length of table (row length and number of
bytes total).
· For numeric attributes, the actual precision of arithmetic
operations and number of significant digits depends on the version of the
platform, compiler, and DBMS. In
general, you should get at least 15 significant digits of accuracy.
· Numeric attributes are limited to 18 digits. The number domain is transformed into a
format of small, integer, or packed based on length:
