In previous article, I have mentioned SQL Server Management Studio (SSMS) Versions but now in this article, I have provided examples to comment query in SQL, which can be useful for you as a database developer to provide comments in query, so other developer can understand why specific query was written and how it is used or why query was used.

So, comments are used in code to understand the piece of code more clearly to explain the sections of the SQL statements, and it can be also be used to prevent the statements of SQL to execute.

You can comment SQL Query in 3 ways

  1. Inline-comments : Comments inside query
  2. Multiline-comments: Multiple query lines are commented in this type.
  3. Single line comments: Single query lines is commented.

sql-comment-single-multi-line-min.png

Single Line comments

Single line comment in SQL can be done using "--Some text--", basically you need to begin your line with two dashes "–"

--Single line comment--
SELECT * FROM [AdventureWorks2012].[dbo].[DatabaseLog]

Single line comment Syntax is same in MySQL, SQL Server and Oracle database, but in MySQL, you need to keep a space after double dashes, like this "-- this is comment --"

Multi Line Comments

Multi line comments, can be used as inline comments also and syntax remains same for SQL Server, MySQL and Oracle database, it starts with "/*" and follow the comment with an asterisk and forward slash basically ends with "*/".

It is C-style comments.

/*This is multi-line comment
which will work in all lines
end here */
SELECT * FROM [AdventureWorks2012].[dbo].Employee
         Where MiddleName = 'E'

Inline Comments

You can use inline comments using "--" after the query or even using "/* */" whichever works for you,  I have taken example of using two dashes "--" comment after query

SELECT * FROM [AdventureWorks2012].[dbo].Employee
         Where MiddleName = 'E' -- these are conditions
		 And  -- with inline-comments
		 Gender = 'F'

and the above examples works perfectly for me in SQL Server.

Or you can also have inline comments as

SELECT * FROM /* Customers; this is comment */ 

SQL comment block

SQL Comment block is considered when you write comment within a Transact-SQL statement using multiple-line comments which must be indicated by /* and */.

A stylistic convention often used for multiple-line comments is to begin the first line with /*, subsequent lines with **, and end with */.

We have given example of it above here is another example

/* multi line comment
another comment */
SELECT * FROM [AdventureWorks2012].[dbo].Employee; 

Sql Server comment shortcut

The keyboard shortcut to comment query or text in SQL Server is CTRL + K, CTRL + C. The keyboard shortcut to uncomment query or text is CTRL + K, CTRL + U.

SQL Query Comment in PostgreSQL

Commenting text or query in PostgresSQL is same as SQL Server, you can start with "/*" enter text or query and then end it with "*/".

/* The following is a very
 * non-trivial SQL code */
SELECT * AS result

That's it, hope this article helps you in understanding comments in SQL and how to use them.

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