Every constant and variable has a datatype that specifies the storage format, constraints, and the valid range of values. The PL/SQL gives a variety of predefined datatypes. The scalar type has no internal components. The composite type has internal components which can be manipulated separately. A reference type holds values, known as the pointers that designate other program items. A LOB type holds values, known as the lob locators that specify the location of large objects stored out-of-line.
Figure represents the predefined datatypes available for your use. The scalar types fall into 4 families that store number, Boolean, character, and date/time data, respectively.