PL/SQL data types are grouped into 4 categories:

► Scalar Data Types: A scalar data type holds a single value.

► Composite Data Types: A composite data type has internal components, such as the elements of an array.

► LOB Data Types: A LOB data type holds a lob locator that specify the location of a large object.

► Reference Data Types: A reference data type holds a pointer that points to another data object.