As mentioned at the beginning of this chapter, the largest area of SQL expansion in the SQL:1999 standard was object-relational support. The SQL:1999 standard specifies new statements, clauses, and expressions in the SQL language in these areas:
- User-defined data types
- Composite (abstract) data types
- Array values
- Overloaded (polymorphic) stored procedures
- Row constructors and table constructors supporting abstract types
- Row-valued and table-valued expressions supporting abstract types
The SQL:1999 extensions don’t exactly match any of the major commercial object- relational DBMS products in their specifics, but the underlying concepts are the same as those illustrated in the earlier sections for specific products. It’s likely that this area of SQL will follow the pattern of others with respect to the standard. Slowly, over a series of major releases, the major DBMS vendors will provide support for the SQL:1999 syntax where it can be added in parallel to their own, well-established proprietary syntax. This process has just begun for SQL:1999 object support. For the next several years, the object-relational capabilities that matter for real-world implementations will continue to be the vendor-proprietary capabilities.
Source: Liang Y. Daniel (2013), Introduction to programming with SQL, Pearson; 3rd edition.