The simplest kind of PL/SQL code is called an anonymous block.
An anonymous block is a block of code that has its own DECLARE/BEGIN/END structure.
Anonymous blocks can either stand on their own (as shown here) or they can sit within any other PL/SQL program.
The general syntax for an anonymous block:
declare
...
...
begin
...
...
exception
...
...
end;
The declaration section defines all variables, cursors, subprograms, and other elements to be used in the code.
The declaration section is optional.
The procedural section contains the main body of the routine.
The procedural section starts with the begin keyword and ends with the exception keyword or the end keyword if you have no exception section.
The procedural section is the only mandatory part of the code.
You must have at least one line of executable code in the procedural section.
You can use the NULL command to indicate that nothing should be executed.
The exception section is also optional.
The exception section allows the program to intercept and process exceptions.