SQL Comment

Documentation is an important component of coding, and SQL is no exception.

There are two main ways to add comments in SQL:

Method 1: Single line

To add a comment that is only across a single line, we would add two dashes '--'. Everything after these two dashe will be considered as a comment and will not be executed. The line break acts as the end of the comment.

Note that you can add the two dashes in the middle of a line. In that instance, everything before the two dashes will still be considered as part of the code and will be executed, while everything after the two dashes is treated as a comment.

Example 1:

An entire line is used as a comment.

Example 2:

Comments can appear anywhere in the code, even in the middle of a SQL block.

In the code above, the HAVING clause will still execute as only the texts after the two dashes are considered as comments.

Method 2: Multiple lines

To add a comment that spans across multiple lines, we would start the comment block with /* and then end the comment block with */. Everything in between these two markers is considered as a comment. There is no strict rule on what needs to go into the comment block. You can leave open lines, have special characters... it doesn't matter.

Example:

In this example, the first three lines are all comments and has no impact on how the code is executed.