Oracle Syntax of a PL/SQL Block

DECLARE
Variable_declarations
BEGIN
Program_code
EXCEPTION
Exception_handlers
END;

Below is the basic structure of the PL/SQL program:

Set serveroutput on
Var1 varchar2(20);
Begin
Var1 := ‘welcome’;
Dbms_output.put_line(var1);
Exception
When others then
Dbms_output.put_line(‘It is an exception’);
End;
/
In the declaration section all the variables and constants are defined.

1. In PL/SQL all the errors are handled in the Exception block.
2. Begin and End are mandatory statements indicating begin and end of the PL/SQL Block.
3. Variables and Constants must be declared first before they can be used.
4. The declaration of variables and constants are alike, but constant definitions must contain the keyword CONSTANT and must be assigned a value as part of the definition. Later on any attempts to assign a value to a constant will result in an error message.
5. Values can be assigned to variables directly using the “:=” assignment operator, by way of a SELECT ... INTO statement or When used as OUT or IN OUT parameter from a procedure.