It's really important when you're writing SQL Server code (or T-SQL in particular) that you add comments to the code where something isn't obvious to someone who's reading it.
Here's an example of comments being used:
There are two ways that comments can be added:
If you put a double-dash on a line, anything after it is a comment.
If you need to comment a block of code, you can put a /* to start the comment and */ to end it. I'm not a fan of block comments in T-SQL because you can't nest one comment inside another comment. With the double-dash method, that's not a problem.
You might also want to use inline comments to just temporarily remove a line of code from a script. For example, if you have a SELECT query that isn't returning what you expect, you might just comment out the WHERE clause to see if that's what the problem is.
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