Oracle Comments.

Preamble

Did you know that you can put comments into SQL statements in Oracle? Comments can appear in one line or be distributed over several lines. Let’s see how this can be done.

There are two syntaxes that you can use to create a comment within your SQL sentences in Oracle/PLSQL.

Syntax for using characters in comments;

Syntax for creating SQL comments in Oracle using characters –:

-- this is where the comment is written

In Oracle, a comment starting with characters — should be at the end of a line in your SQL statement with a line break after it. This comment method can only take up one line in your SQL and should be at the end of a line.

Syntax for using /* and */ in comments

Syntax for creating an SQL comment in Oracle using the characters /* and */:

/* comment is written here */

In Oracle, a comment that starts with /* and ends with */ can be anywhere in your SQL sentence.

This method of commenting can take several lines within your SQL sentence.

An example comment on a single line

You can create an SQL comment on one line in an SQL sentence in Oracle/PLSQL.

Consider an example of an SQL comment that shows an SQL comment on one line:

SELECT count(suppls.suppl_id)
/* number of suppliers */
FROM suppls;

This SQL comment, appears in the middle of the line:

SELECT /* number of suppliers */ count(suppls.suppl_id)
FROM suppls;

This SQL comment, appears at the end of the line:

SELECT count(suppls.suppl_id) /* number of suppliers */
FROM suppls;

or

SELECT count(suppls.suppl_id) -- number of suppliers
FROM suppls;

An example of a comment on several lines

In Oracle, you can create an SQL comment that covers several lines in your SQL sentence.

SELECT count(suppls.suppl_id)
/*
* number of suppliers
* a comment covers several lines in your SQL sentence.
*/
FROM suppls;

This SQL comment is spread over several lines in Oracle – in this example, it is stretched over 4 lines.

In Oracle, you can also create an SQL comment that covers several lines using the following syntax:

SELECT count(suppls.suppl_id) /* number of suppliers
a comment that covers several lines in your SQL sentence */
FROM suppls;

Oracle/PLSQL will assume that everything after the /* character is a comment until it reaches the */ character, even if it covers several lines within the SQL sentence. Thus, in this example, an SQL comment will cover 2 lines.

Oracle Tutorial; Add Comment on a Table and Column, Remove Comment

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