REGEXP_LIKE (Transact-SQL) preview

Applies to: SQL Server 2025 (17.x) Preview Azure SQL Database Azure SQL Managed Instance SQL database in Microsoft Fabric Preview

Indicates if the regular expression pattern matches in a string.

REGEXP_LIKE 
     (
      string_expression,
      pattern_expression [, flags ]
     )

REGEXP_LIKE requires database compatibility level 170 and above. If the database compatibility level is lower than 170, REGEXP_LIKE is not available. Other regular expression scalar functions are available at all compatibility levels.

You can check compatibility level in the sys.databases view or in database properties. You can change the compatibility level of a database with the following command:

ALTER DATABASE [DatabaseName] SET COMPATIBILITY_LEVEL = 170;

Arguments

string_expression

An expression of a character string.

Can be a constant, variable, or column of character string.

Data types: char, nchar, varchar, or nvarchar.

pattern_expression

Regular expression pattern to match. Usually a text literal.

Data types: char, nchar, varchar, or nvarchar. pattern_expression supports a maximum character length of 8,000 bytes.

flags

One or more characters that specify the modifiers used for searching for matches. Type is varchar or char, with a maximum of 30 characters.

For example, ims. The default is c. If an empty string (' ') is provided, it will be treated as the default value ('c'). Supply c or any other character expressions. If flag contains multiple contradictory characters, then SQL Server uses the last character.

For example, if you specify ic the regex returns case-sensitive matching.

If the value contains a character other than those listed at Supported flag values, the query returns an error like the following example:

Invalid flag provided. '<invalid character>' are not valid flags. Only {c,i,s,m} flags are valid.

Supported flag values

Return value

Boolean value. true or false.

Remarks

SARGability support

REGEXP_LIKE supports SARGability when the pattern begins with anchor ^ and also the patterns that include quantifiers such as *, +, ?, {m}, {m,}, and {m,n}, for example, ^ab+ or ^ab* etc. This allows the query optimizer to use index seek operations, improving query performance. However, regular expressions do not honor collation rules, which may lead to differences in behavior when compared to other string comparison functions like LIKE, especially on indexed columns with language-specific collations.

For example, in Turkish collation, the characters i and I are treated distinctly even in the case-insensitive collation due to language-specific rules.

Cardinality estimation

To enhance the accuracy of cardinality estimation for the REGEXP_LIKE function, you can use the ASSUME_FIXED_MIN_SELECTIVITY_FOR_REGEXP and ASSUME_FIXED_MAX_SELECTIVITY_FOR_REGEXP query hints to adjust the default selectivity values. For more information, see Query hints.

These query hints are also integrated with Cardinality estimation (CE) feedback. The CE feedback model automatically identifies queries using REGEXP_LIKE function where there is a significant difference between estimated and actual row counts. It then applies the appropriate selectivity hint at the query level to improve plan quality without requiring manual input.

To disable the automatic feedback behavior, enable Trace Flag 16268.

Examples

Select all records from the EMPLOYEES table where the first name starts with A and ends with Y

SELECT * FROM EMPLOYEES WHERE REGEXP_LIKE (FIRST_NAME, '^A.*Y$'); 

Select all records from the ORDERS table where the order date is in February 2020.

SELECT * FROM ORDERS WHERE REGEXP_LIKE (ORDER_DATE, '2020-02-\d\d'); 

Select all records from the PRODUCTS table where the product name contains at least three consecutive vowels

SELECT * FROM PRODUCTS WHERE REGEXP_LIKE (PRODUCT_NAME, '[AEIOU]{3,}'); 

Create employees table with CHECK constraints for Email and Phone_Number columns.

DROP TABLE IF EXISTS EMPLOYEES;

CREATE TABLE EMPLOYEES (  
    ID INT IDENTITY(101,1),  
    [Name] VARCHAR(150),  
    Email VARCHAR(320)  
    CHECK (REGEXP_LIKE(Email, '^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}$')),  
    Phone_Number NVARCHAR(20)  
    CHECK (REGEXP_LIKE (Phone_Number, '^(\d{3})-(\d{3})-(\d{4})$'))  
);

Here's an example that demonstrates SARGable vs non-SARGable use of the REGEXP_LIKE function with Turkish collation.

-- Create a temporary table with Turkish collation and and an index
CREATE TABLE #Users (
    Username NVARCHAR(100) COLLATE Turkish_100_CI_AS_SC_UTF8 NOT NULL,
    INDEX idx_username (Username)
);

-- Insert sample data
INSERT INTO #Users (Username)
VALUES (N'i'),    -- lowercase i
       (N'I'),    -- uppercase dotless I
       (N'İ'),    -- uppercase dotted İ
       (N'abc');

-- SARGable pattern: starts with ^ and uses quantifier
-- This will use index seek if applicable, but REGEXP_LIKE ignores collation
-- So 'i' and 'I' are treated as different characters
SELECT 'SARGable' AS PatternType, * 
FROM #Users
WHERE REGEXP_LIKE(Username, '^i');

-- Non-SARGable pattern: does not start with ^
-- REGEXP_LIKE performs full scan, and matches are case-insensitive since 'i' flag is supplied
-- So both 'i' and 'I' will match
SELECT 'Non-SARGable' AS PatternType, * 
FROM #Users
WHERE REGEXP_LIKE(Username, 'i','i');

-- Cleanup
DROP TABLE #Users;

Related content

• Work with regular expressions
• Regular expressions functions (Transact-SQL)