Unlocking the Power of LIKE: A Beginner's Guide to Safe String Escaping in SQL Server

• %: Percent sign - Matches any single character.
• []: Square brackets - Used to define a set of characters to match.
• -: Hyphen - Represents a range of characters within square brackets (e.g., [a-z]).

Escaping with Backslash:

To prevent these characters from being interpreted as special operators, you need to escape them using a backslash (\) character before the specific character.

Example:

Imagine you want to search for names containing the literal character %. Without escaping, the query:

SELECT * FROM Customers WHERE Name LIKE '%';

would return all names in the Customers table, regardless of their content, because % acts as a wildcard, matching any character sequence.

To search for names containing the literal %, you need to escape it:

SELECT * FROM Customers WHERE Name LIKE '\%';

This query will now correctly search for names with the exact character %.

Alternative: Square Brackets for [ and ]

For the characters [ and ], you can alternatively enclose them within square brackets to treat them as literal characters. This approach avoids the need for escaping with a backslash:

SELECT * FROM Customers WHERE Name LIKE '[%]';

Best Practices:

• Always escape special characters when using them as literal values within the LIKE pattern.
• Consider using parameterized queries to prevent SQL injection vulnerabilities. Parameterized queries separate the data from the T-SQL code, making it safer and more secure.
• Be mindful of the context: If you're unsure whether a character needs escaping, it's generally better to err on the side of caution and escape it.