DB2 object relational extensions
With the object extensions of DB2®, you can incorporate object-oriented concepts and methodologies into your relational database by extending DB2 with richer sets of data types and functions.
With those extensions, you can store instances of object-oriented data types in columns of tables and operate on them using functions in SQL statements. In addition, you can control the types of operations that users can perform on those data types.
- Large objects (LOBs)
The VARCHAR, VARGRAPHIC, and VARBINARY data types have a storage limit of 32 KB. Although this might be sufficient for small- to medium-size text data, applications often need to store large text documents. They might also need to store a wide variety of additional data types such as audio, video, drawings, mixed text and graphics, and images. DB2 provides three data types to store these data objects as strings of up to 2 GB - 1 in size. The three data types are binary large objects (BLOBs), character large objects (CLOBs), and double-byte character large objects (DBCLOBs).
For a detailed discussion of LOBs, see Storing LOB data in a table and Large objects (LOBs).
- Distinct types
A distinct type is a user-defined data type that shares its internal representation with a built-in data type but is considered to be a separate and incompatible type for semantic purposes. For example, you might want to define a picture type or an audio type, both of which have quite different semantics, but which use the built-in data type BLOB for their internal representation.
For a detailed discussion of distinct types, see Distinct types.
- User-defined functions
The built-in functions that are supplied with DB2 are a useful set of functions, but they might not satisfy all of your requirements. For those cases, you can use user-defined functions. For example, a built-in function might perform a calculation you need, but the function does not accept the distinct types you want to pass to it. You can then define a function based on a built-in function, called a sourced user-defined function, that accepts your distinct types. You might need to perform another calculation in your SQL statements for which no built-in function exists. In that situation, you can define and write an SQL function or an external function.
For a detailed discussion of user-defined functions, see Steps to creating and using a user-defined function.