PL/SQL Lexical Unit

 PL/SQL Lexical Unit  

     A programming language has lexical units that are the building blocks of the language.

    PL/SQL lexical units fall within one of the following five groups:
    1) Identifiers must begin with a letter and may be up to 30 characters long.
    2) Reserved words are words that PL/SQL saves for its own use (such as BEGIN, END, and SELECT).
    3) Delimiters are characters that have special meaning to PL/SQL, such as arithmetic operators and quotation marks.
    4) Literals are values (character, numeric, or Boolean [true/false]) that are not identifiers. 123, "Declaration of Independence," and FALSE are examples of literals.
    5) Comments can be either single-line comments (--) or multi line comments (/* */).

 Identifiers/Variables :  

    Variables are used to hold a temporary value.Variables must begin with a letter .

 Example :  

 l_student_id 
 l_last_name
 l_LAST_NAME
 apt_#     

 Reserved Words :  

    These are the words that can not be used as a variable or literals.

 Example :  

 BEGIN,DECLARE,END,LOOP,CASE,SELECT,INTO,FROM  

 Example :  

    Smallest program in PL/SQL.

 BEGIN
   null;     
 end;