19.5 SQL-99 Data Types

   The data types defined by the SQL-99 specification are created within CWM as instances of the Relational package’s SQLSimpleType metaclass. These data type instances are a superset of those defined by the SQL-92 specification and follow the SQL-99 specification’s Data_Type_Descriptor information. Practical implementations of SQL-based systems will have variations on the types presented here; consult relevant product information for details.

   The SQL-99 data type instances provide a number of examples of the use of “parameterized? types. Because the CWM Relational package separates the notions of data type and column, the data type instances do not contain all seemingly relevant data type parameters. Rather, the Column instances associated with a particular Table instance contain the values of some parameters. For example, for a Column instance of declared data type DECIMAL(5, 2), the precision (“5?) and scale (“2?) would be recorded in the attributes Column::precision and Column::scale, respectively, whereas the DECIMAL data type instance would have its SQLSimpleType::precisionRadix attribute set to the value 10, meaning that the precision and scale values are stored as base-10 numeric values. Similarly, a Column instance declared as CHARACTER(80) would have the Column::length attribute set to 80 while the CHARACTER data type’s SQLSimpleType::characterOctetLength attribute would be set to value 8 indicating that the data type contains 8-bit character codes.