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Asked: 2024-09-27T00:06:37+05:30 In:

how to comment in sql query

I’ve recently started working with SQL for some database management tasks, and I keep encountering a bit of confusion about how to properly add comments to my SQL queries. I understand that comments can be useful for explaining complex parts of my code or adding notes to myself or others who might work on the queries in the future. However, I’m not entirely sure about the syntax for adding these comments.

I’ve seen various SQL scripts, and I notice some queries have text within a pair of slashes or between a pair of dashes, but I’m unsure of the correct way to do this across different SQL systems. Are there different comment styles based on whether I’m using MySQL, SQL Server, or PostgreSQL? Also, what’s the difference between single-line comments and multi-line comments? I’m concerned that I might be using an incorrect format, which could lead to errors in my scripts.

Could someone provide me with a clear explanation of how to comment effectively in SQL queries, including examples for both single-line and multi-line comments? Any insights on best practices would also be appreciated!

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    2 Answers


    1. In SQL, commenting is a vital practice that enhances code readability and maintainability, particularly in complex queries. You can use two primary methods for commenting: single-line comments and multi-line comments. To create a single-line comment, simply prepend your comment with two dashes (`–`). For example: `SELECT * FROM customers — This retrieves all customer records`. Alternatively, you can use the `#` symbol for single-line comments in some database systems like MySQL. In contrast, if you need to comment out a block of text or multiple lines, you can use the `/* comment here */` syntax. This can be quite useful during troubleshooting or when you want to provide more in-depth explanations about the code logic.

      Knowing when and how to comment is just as important as the comments themselves. Comments should be precise and relevant, helping other developers (or even your future self) understand the context and intent behind complex queries or logic. Avoid over-commenting trivial code that is self-explanatory; instead, focus on providing insights into the reason behind specific choices and how different components interact. Effective comments will convey critical information without cluttering the code, allowing future modifications to be carried out with a clearer understanding of the code’s purpose and functionality.

    2. So, like, if you wanna add comments in your SQL query, it’s kinda like writing little notes to yourself, right? So, you can do it in a couple of ways. At least, that’s what I think!

      First, you can just use two dashes -- at the beginning of a line, and everything after those dashes will be ignored by SQL. It’s like saying, “Hey SQL, just ignore this part.” Like:

          SELECT * FROM users
    -- This part is just a comment, nothing to see here
    WHERE age > 21;

      Or, if you wanna write a longer comment, you can use /* to start and */ to end your comment. It’s like wrapping your comment in a blanket!:

          SELECT * FROM products
    /* 
       This is a longer comment
       and can be pretty helpful
       to explain your logic or whatever
    */
    WHERE price < 100;

      Yeah, that’s pretty much it! Comments don’t change the way things work; they’re just there to help you remember or explain stuff, you know?

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