SQL Comment

How do you add comments in SQL?

SQL comments are used to explain SQL code. They are ignored by the database system and are helpful for documentation. Comments improve readability and maintainability of queries.

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Description

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Example H3

Comments in SQL are annotations within your code that are ignored by the database system when executing queries. They serve as valuable documentation, making your code easier to understand and maintain, especially in larger projects. They are crucial for explaining complex logic, clarifying the purpose of different sections, and helping other developers (or your future self) comprehend the code's functionality. Comments are particularly helpful when working with intricate queries or procedures. They allow you to add explanatory notes directly into the code, enhancing its readability and maintainability. This is a fundamental aspect of writing clean and understandable SQL code.

Why SQL Comment is important

Comments are essential for maintaining and understanding SQL codebases. They improve collaboration among developers and make it easier to modify or debug queries in the future. Clear comments reduce the time spent deciphering complex logic.

SQL Comment Example Usage


-- Sample table: Orders
CREATE TABLE Orders (
    OrderID INT PRIMARY KEY,
    OrderDate DATE,
    CustomerName VARCHAR(50)
);

INSERT INTO Orders (OrderID, OrderDate, CustomerName)
VALUES
(1, '2023-01-15', 'Alice'),
(2, '2023-02-20', 'Bob'),
(3, '2023-01-10', 'Charlie'),
(4, '2023-03-05', 'David'),
(5, '2023-01-25', 'Eve');

-- Query to find orders placed between January 10, 2023, and January 25, 2023 (inclusive)
SELECT OrderID, OrderDate, CustomerName
FROM Orders
WHERE OrderDate BETWEEN '2023-01-10' AND '2023-01-25';

SQL Comment Syntax

Common Mistakes

Forgetting to use comments to explain complex queries.
Using comments that are too brief or vague, failing to provide sufficient context.
Not using consistent commenting styles across the codebase.

Frequently Asked Questions (FAQs)

Why should I always include comments in complex SQL queries?

Comments act as in-line documentation that explain business logic, join conditions, and transformation steps. When queries become long or nested, these annotations let any developer quickly understand why something is written a certain way without reverse-engineering the entire statement. Because the database engine ignores comment lines, they add zero performance overhead while massively improving readability.

How do SQL comments boost long-term maintainability of a codebase?

Well-written comments clarify the purpose of tables, columns, and filters, making it easier to troubleshoot bugs or refactor queries months later. They shorten onboarding time for new team members and reduce the risk of accidentally breaking production logic. In large projects, comments essentially serve as living documentation embedded directly in your SQL version control, keeping knowledge close to the code that depends on it.

Does a modern editor like Galaxy make working with SQL comments easier?

Yes. Galaxy’s lightning-fast SQL editor and context-aware AI copilot recognize comment blocks, auto-format them, and can even suggest descriptive comment text as you write. This means you document queries while staying in flow, share them in Galaxy Collections, and ensure every teammate sees the same well-commented, endorsed version—no more pasting undocumented SQL in Slack.