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Unveiling the Mystery of T-SQL Special Characters

SQL is the de facto language for managing and querying structured data, and within the SQL family, Transact-SQL (T-SQL) stands as the sturdy backbone, particularly for SQL Server. T-SQL developers and data analysts wade through thousands of lines of code, each with its own subtle nuances. Amidst the sea of queries and scripts, special characters play a pivotal yet understated role. Journey with us to demystify the enigmatic world of T-SQL special characters and discover how to wield them with finesse.

Special Characters Waltzing in the T-SQL Universe

T-SQL, like any programming language, has a repertoire of special characters. These aren’t your everyday letters or numbers. They’re the ampersands, brackets, colons, and more that give the language its structure, enabling everything from commentation to streamlining complex operations.

The Ever-Present ‘SELECT’ and Its Semicolon

The humble semicolon is an often overlooked T-SQL character. SQL statements typically end with a semicolon – it’s the language’s way of saying “I’m done here.” However, SQL Server became a bit less lenient, making semicolons a requirement in 2008. Developers often work with legacy systems that don’t require semicolons, leading to a dash of confusion in an otherwise straightforward command.

Single Quote (”): Used to delimit string literals. For example:

SELECT ‘Hello, World!’ AS Greeting;

Double Quote (“”): Typically used as an identifier delimiter, especially when dealing with identifiers that contain spaces or special characters. For example:

SELECT "First Name", "Last Name" FROM Employee;

Square Brackets ([]): Used as an alternative to double quotes for delimiting identifiers. Square brackets are also used to escape special characters in identifiers. For example:

SELECT [First Name], [Last Name] FROM [Employee Table];

Ampersand (&): Used for bitwise AND operations. For example:

DECLARE @result INT; SET @result = 5 & 3; -- This sets @result to 1

Percent (%): Used as a wildcard character in LIKE patterns to represent any sequence of characters. For example:

SELECT * FROM Products WHERE ProductName LIKE '%apple%';

Underscore (_) and Square Brackets ([]): Both used as wildcard characters in LIKE patterns to represent any single character. For example:

SELECT * FROM Employees WHERE LastName LIKE 'Smi_';

Asterisk (*): Used as a wildcard character in SELECT statements to select all columns or as a multiplication operator. For example:

SELECT  FROM Employees; -- Selects all columns SELECT FirstName  Salary AS TotalPay FROM Employees; -- Calculates total pay

Plus (+) and Minus (-): Used as addition and subtraction operators, respectively. For example:

SELECT 5 + 3 AS Sum; SELECT 10 - 4 AS Difference;

Forward Slash (/) and Backward Slash (): Used as division and escape characters, respectively. For example:

SELECT 10 / 2 AS DivisionResult; SELECT 'It''s raining' AS TextWithSingleQuote; 

These are some of the commonly used special characters in T-SQL. Understanding their usage is essential for writing effective and correct SQL queries.


In T-SQL, you can use comments to document your code, provide explanations, or temporarily disable certain parts of your script without affecting its functionality. Here’s how you can make comments in T-SQL and some best practices:

Single-Line Comments:

Single-line comments start with two consecutive hyphens (–) and continue until the end of the line. They are useful for adding short explanations or notes within your code.

-- This is a single-line comment
SELECT * FROM Employees; -- This is another single-line comment

Multi-Line Comments:

Multi-line comments start with /* and end with */. They can span across multiple lines and are useful for longer explanations or temporarily disabling blocks of code.

This is a multi-line comment.
It can span across multiple lines.

/* SELECT * FROM Products;
   This query is commented out for now. */

Best Practices for Using Comments:

Be Clear and Concise: Write comments that are easy to understand and provide clear explanations of the code’s purpose or behavior.

Use Comments Sparingly: While comments are helpful for documenting your code, avoid over-commenting. Focus on adding comments where they add value, such as complex logic or business rules.

Update Comments Regularly: Keep your comments up-to-date with any changes made to the code. Outdated comments can be misleading and lead to confusion.

Follow a Consistent Style: Establish a consistent style for writing comments across your codebase. This makes it easier for other developers to understand and maintain the code.

Avoid Redundant Comments: Avoid adding comments that simply restate what the code is doing. Instead, focus on explaining why certain decisions were made or providing context that isn’t immediately obvious from the code itself.

Use Comments for Documentation: Comments can also serve as documentation for your database objects, such as tables, columns, and stored procedures. Use comments to describe the purpose of each object and any relevant details.

Consider Future Maintenance: Write comments with future maintenance in mind. Think about what information would be helpful for someone else (or your future self) who needs to understand or modify the code.

By following these best practices, you can effectively use comments in your T-SQL code to improve its readability, maintainability, and overall quality.

Final Thoughts: Mastery Over Special Characters

Special characters in T-SQL can sometimes feel like the puzzle pieces that never quite fit, but with practice and patience, they will become invaluable tools for crafting precise and powerful queries. Remember to consult official documentation for the specific version you’re working with, and never stop experimenting with the different ways these characters can be utilized.

For the SQL developer, the journey of understanding and mastering special characters is perpetual. As languages evolve and data grows more complex, these symbols will continue to take on new meanings and functionalities. So, embrace the T-SQL special characters – they might just be your key to unlocking the database kingdom.

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