What is COMMENTS in SQL?

As is any programming languages comments matter a lot in SQL also. In this set we will learn about writing comments in any SQL snippet.

Comments can be written in the following three formats:

1. Single line comments.
2. Multi line comments
3. In line comments

• Single line comments: Comments starting and ending in a single line are considered as single line comments.
  Line starting with ‘–‘ is a comment and will not be executed.
  Syntax:

  -- single line comment
  -- another comment
  SELECT * FROM Customers; 
  

• Multi line comments: Comments starting in one line and ending in different line are considered as multi line comments. Line starting with ‘/*’ is considered as starting point of comment and are terminated when ‘*/’ is encountered.
  Syntax:

  /* multi line comment
  another comment */
  SELECT * FROM Customers; 
  

• In line comments: In line comments are an extension of multi line comments, comments can be stated in between the statements and are enclosed in between ‘/*’ and ‘*/’.
  Syntax:

  SELECT * FROM /* Customers; */ 
  

  More examples:

  Multi line comment ->
  /* SELECT * FROM Students;
  SELECT * FROM STUDENT_DETAILS;
  SELECT * FROM Orders; */
  SELECT * FROM Articles; 
  
  In line comment ->
  SELECT * FROM Students;
  SELECT * FROM /* STUDENT_DETAILS;
  SELECT * FROM Orders;
  SELECT * FROM */ Articles;