In SQL Comments, you can comment your code just like any other language. Comments can appear on a single line or span across multiple lines. Let\’s explore how to comment your SQL statements.
Syntax
There are two syntaxes that you can use to create a comment in SQL.
Syntax Using — symbol
The syntax for creating a comment in SQL using — symbol is:
— comment goes here
A comment started with — symbol must be at the end of a line in your SQL statement with a line break after it. This method of commenting can only span a single line within your SQL and must be at the end of the line.
Syntax Using /* and */ symbols
The syntax for creating a comment in SQL using /* and */ symbols is:
/* comment goes here */
A comment that starts with /* symbol and ends with */ and can be anywhere in your SQL statement. This method of commenting can span several lines within your SQL.
Example – Comment on a Single Line
Let\’s look at an example that shows how to create a comment in SQL that is on a single line.
For example:
Here is a comment that appears on its own line in SQL:
SELECT websites.site_name
/* comments */
FROM websites;
Here is a comment that appears in the middle of the line in SQL:
SELECT /* comments */ websites.site_name
FROM websites;
Here is a comment that appears at the end of the line in SQL:
SELECT websites.site_name /* comments */
FROM websites;
or
SELECT websites.site_name — comments
FROM websites;
Example – Comment on Multiple Lines
You can also create a comment that spans multiple lines in your SQL statement.
For example:
SELECT websites.site_name
/*
* comments
* Purpose: To show a comment that spans multiple lines in your SQL statement.
*/
FROM websites;
This comment spans across multiple lines in SQL and in this example, it spans across 4 lines.
You can also create a comment that spans multiple lines using this syntax:
SELECT websites.site_name /* comments
Purpose: To show a comment that spans multiple lines in your SQL statement. */
FROM websites;
SQL will assume that everything after the /* symbol is a comment until it reaches the */ symbol, even if it spans multiple lines within the SQL statement. So in this example, the comment will span across 2 lines.