VARIABLE TYPES IN PL/SQL:

1. All PL/SQL variables have a datatype specifying
   a) Storage Format b) Constraints c) Valid range
2. PL/SQL supports four datatypes categories.
      a) Scalar Datatypes:
        ->They hold a single value.
        ->Main datatypes are those that correspond to column types in Oracle Server Table.
        ->Supports Boolean Variables.
      b) Composite Datatypes:
        ->Records allows groups of fields to be defined and manipulated in PL/SQL blocks.
      c) Reference Datatypes:
        ->They hold values, called pointers, which designate other program items.
      d) LOB Datatypes:
        ->They hold values called locations,specifying the location of large objects that are stored out of line.