SQL string matching

In SQL, string matching refers to the process of finding and retrieving data from a database based on specific patterns or conditions within character strings. SQL provides various tools and functions to perform string matching operations, allowing users to search for specific substrings, patterns, or values within text columns. Here are some common techniques and functions used for string matching in SQL:

LIKE Operator

The LIKE operator is used to perform pattern matching in SQL. It allows you to search for a specified pattern in a column. The basic syntax is as follows:

SELECT column_name(s)
FROM table_name
WHERE column_name LIKE pattern;

%: Represents zero or more characters.
_: Represents a single character.


FROM employees
WHERE last_name LIKE 'Sm%';

This query retrieves all employees whose last names start with “Sm.”

Wildcard Characters:

Wildcard characters (% and _) are used with the LIKE operator for more flexible string matching. For example:

% (percent sign): Represents zero or more characters.
_ (underscore): Represents a single character.


FROM products
WHERE product_name LIKE 'App%e';

This query retrieves products with names starting with “App” and ending with “e.”

REGEXP (Regular Expressions):

Some database systems, such as MySQL and PostgreSQL, support regular expressions for advanced pattern matching. The REGEXP operator is used for this purpose.

Example (MySQL):

FROM customers
WHERE customer_name REGEXP '^[A-D]';

This query retrieves customers whose names start with the letters A, B, C, or D.


SQL Server provides functions like CHARINDEX and PATINDEX to find the starting position of a substring in a string.


SELECT CHARINDEX('is', column_name) as position
FROM table_name;

SELECT PATINDEX('%is%', column_name) as position
FROM table_name;

This query returns the position of the substring “is” in the specified column.


String concatenation can be used to combine multiple columns or literals for matching.


FROM employees
WHERE CONCAT(first_name, ' ', last_name) = 'John Doe';

This query retrieves employees with the full name “John Doe.”

String matching in SQL provides powerful tools for searching and filtering data based on textual patterns, making it a crucial aspect of database querying and analysis. The specific techniques and functions available may vary slightly depending on the database management system being used.