LIKE (Transact-SQL)
Determines whether a specific character string matches a specified pattern. A pattern can include regular characters and wildcard characters. During pattern matching, regular characters must exactly match the characters specified in the character string. However, wildcard characters can be matched with arbitrary fragments of the character string. Using wildcard characters makes the LIKE operator more flexible than using the = and != string comparison operators. If any one of the arguments is not of character string data type, the SQL Server Database Engine converts it to character string data type, if it is possible.
.gif "Ikona łącza do tematu")
Transact-SQL Syntax Conventions
Składnia
match_expression [ NOT ] LIKE pattern [ ESCAPE escape_character ]
Arguments
match_expression
Is any valid expression of character data type.pattern
Is the specific string of characters to search for in match_expression, and can include the following valid wildcard characters. pattern can be a maximum of 8,000 bytes.Wildcard character
Description
Example
%
Any string of zero or more characters.
WHERE title LIKE '%computer%' finds all book titles with the word 'computer' anywhere in the book title.
_ (underscore)
Any single character.
WHERE au_fname LIKE '_ean' finds all four-letter first names that end with ean (Dean, Sean, and so on).
[ ]
Any single character within the specified range ([a-f]) or set ([abcdef]).
WHERE au_lname LIKE '[C-P]arsen' finds author last names ending with arsen and starting with any single character between C and P, for example Carsen, Larsen, Karsen, and so on. In range searches, the characters included in the range may vary depending on the sorting rules of the collation.
[^]
Any single character not within the specified range ([^a-f]) or set ([^abcdef]).
WHERE au_lname LIKE 'de[^l]%' all author last names starting with de and where the following letter is not l.
escape_character
Is a character that is put in front of a wildcard character to indicate that the wildcard should be interpreted as a regular character and not as a wildcard. escape_character is a character expression that has no default and must evaluate to only one character.
Result Types
Boolean
Result Value
LIKE returns TRUE if the match_expression matches the specified pattern.
Uwagi
When you perform string comparisons by using LIKE, all characters in the pattern string are significant. This includes leading or trailing spaces. If a comparison in a query is to return all rows with a string LIKE 'abc ' (abc followed by a single space), a row in which the value of that column is abc (abc without a space) is not returned. However, trailing blanks, in the expression to which the pattern is matched, are ignored. If a comparison in a query is to return all rows with the string LIKE 'abc' (abc without a space), all rows that start with abc and have zero or more trailing blanks are returned.
A string comparison using a pattern that contains char and varchar data may not pass a LIKE comparison because of how the data is stored. You should understand the storage for each data type and where a LIKE comparison may fail. The following example passes a local char variable to a stored procedure and then uses pattern matching to find all of the employees whose last names start with a specified set of characters.
USE AdventureWorks2012;
GO
CREATE PROCEDURE FindEmployee @EmpLName char(20)
AS
SELECT @EmpLName = RTRIM(@EmpLName) + '%';
SELECT p.FirstName, p.LastName, a.City
FROM Person.Person p JOIN Person.Address a ON p.BusinessEntityID = a.AddressID
WHERE p.LastName LIKE @EmpLName;
GO
EXEC FindEmployee @EmpLName = 'Barb';
GO
In the FindEmployee procedure, no rows are returned because the char variable (@EmpLName) contains trailing blanks whenever the name contains fewer than 20 characters. Because the LastName column is varchar, there are no trailing blanks. This procedure fails because the trailing blanks are significant.
However, the following example succeeds because trailing blanks are not added to a varchar variable.
USE AdventureWorks2012;
GO
CREATE PROCEDURE FindEmployee @EmpLName varchar(20)
AS
SELECT @EmpLName = RTRIM(@EmpLName) + '%';
SELECT p.FirstName, p.LastName, a.City
FROM Person.Person p JOIN Person.Address a ON p.BusinessEntityID = a.AddressID
WHERE p.LastName LIKE @EmpLName;
GO
EXEC FindEmployee @EmpLName = 'Barb';
Here is the result set.
FirstName LastName City
---------- -------------------- ---------------
Angela Barbariol Snohomish
David Barber Snohomish
(2 row(s) affected)
Pattern Matching by Using LIKE
LIKE supports ASCII pattern matching and Unicode pattern matching. When all arguments (match_expression, pattern, and escape_character, if present) are ASCII character data types, ASCII pattern matching is performed. If any one of the arguments are of Unicode data type, all arguments are converted to Unicode and Unicode pattern matching is performed. When you use Unicode data (nchar or nvarchar data types) with LIKE, trailing blanks are significant; however, for non-Unicode data, trailing blanks are not significant. Unicode LIKE is compatible with the ISO standard. ASCII LIKE is compatible with earlier versions of SQL Server.
The following is a series of examples that show the differences in rows returned between ASCII and Unicode LIKE pattern matching.
-- ASCII pattern matching with char column
CREATE TABLE t (col1 char(30));
INSERT INTO t VALUES ('Robert King');
SELECT *
FROM t
WHERE col1 LIKE '% King'; -- returns 1 row
-- Unicode pattern matching with nchar column
CREATE TABLE t (col1 nchar(30));
INSERT INTO t VALUES ('Robert King');
SELECT *
FROM t
WHERE col1 LIKE '% King'; -- no rows returned
-- Unicode pattern matching with nchar column and RTRIM
CREATE TABLE t (col1 nchar (30));
INSERT INTO t VALUES ('Robert King');
SELECT *
FROM t
WHERE RTRIM(col1) LIKE '% King'; -- returns 1 row
[!UWAGA]
LIKE comparisons are affected by collation. For more information, see COLLATE (Transact-SQL).
Using the % Wildcard Character
If the LIKE '5%' symbol is specified, the Database Engine searches for the number 5 followed by any string of zero or more characters.
For example, the following query shows all dynamic management views in the AdventureWorks2012 database, because they all start with the letters dm.
USE AdventureWorks2012;
GO
SELECT Name
FROM sys.system_views
WHERE Name LIKE 'dm%';
GO
To see all objects that are not dynamic management views, use NOT LIKE 'dm%'. If you have a total of 32 objects and LIKE finds 13 names that match the pattern, NOT LIKE finds the 19 objects that do not match the LIKE pattern.
You may not always find the same names with a pattern such as LIKE '[^d][^m]%'. Instead of 19 names, you may find only 14, with all the names that start with d or have m as the second letter eliminated from the results, and the dynamic management view names. This is because match strings with negative wildcard characters are evaluated in steps, one wildcard at a time. If the match fails at any point in the evaluation, it is eliminated.
Using Wildcard Characters As Literals
You can use the wildcard pattern matching characters as literal characters. To use a wildcard character as a literal character, enclose the wildcard character in brackets. The following table shows several examples of using the LIKE keyword and the [ ] wildcard characters.
Symbol |
Meaning |
|---|---|
LIKE '5[%]' |
5% |
LIKE '[_]n' |
_n |
LIKE '[a-cdf]' |
a, b, c, d, or f |
LIKE '[-acdf]' |
-, a, c, d, or f |
LIKE '[ [ ]' |
[ |
LIKE ']' |
] |
LIKE 'abc[_]d%' |
abc_d and abc_de |
LIKE 'abc[def]' |
abcd, abce, and abcf |
Pattern Matching with the ESCAPE Clause
You can search for character strings that include one or more of the special wildcard characters. For example, the discounts table in a customers database may store discount values that include a percent sign (%). To search for the percent sign as a character instead of as a wildcard character, the ESCAPE keyword and escape character must be provided. For example, a sample database contains a column named comment that contains the text 30%. To search for any rows that contain the string 30% anywhere in the comment column, specify a WHERE clause such as WHERE comment LIKE '%30!%%' ESCAPE '!'. If ESCAPE and the escape character are not specified, the Database Engine returns any rows with the string 30.
If there is no character after an escape character in the LIKE pattern, the pattern is not valid and the LIKE returns FALSE. If the character after an escape character is not a wildcard character, the escape character is discarded and the character following the escape is treated as a regular character in the pattern. This includes the percent sign (%), underscore (_), and left bracket ([) wildcard characters when they are enclosed in double brackets ([ ]). Also, within the double bracket characters ([ ]), escape characters can be used and the caret (^), hyphen (-), and right bracket (]) can be escaped.
0x0000 (char(0)) is an undefined character in Windows collations and cannot be included in LIKE.
Examples
A. Using LIKE with the % wildcard character
The following example finds all telephone numbers that have area code 415 in the PersonPhone table.
USE AdventureWorks2012;
GO
SELECT p.FirstName, p.LastName, ph.PhoneNumber
FROM Person.PersonPhone AS ph
INNER JOIN Person.Person AS p
ON ph.BusinessEntityID = p.BusinessEntityID
WHERE ph.PhoneNumber LIKE '415%'
ORDER by p.LastName;
GO
Here is the result set.
FirstName LastName Phone
----------------- ------------------- ------------
Ruben Alonso 415-555-124
Shelby Cook 415-555-0121
Karen Hu 415-555-0114
John Long 415-555-0147
David Long 415-555-0123
Gilbert Ma 415-555-0138
Meredith Moreno 415-555-0131
Alexandra Nelson 415-555-0174
Taylor Patterson 415-555-0170
Gabrielle Russell 415-555-0197
Dalton Simmons 415-555-0115
(11 row(s) affected)
B. Using NOT LIKE with the % wildcard character
The following example finds all telephone numbers in the PersonPhone table that have area codes other than 415.
USE AdventureWorks2012;
GO
SELECT p.FirstName, p.LastName, ph.PhoneNumber
FROM Person.PersonPhone AS ph
INNER JOIN Person.Person AS p
ON ph.BusinessEntityID = p.BusinessEntityID
WHERE ph.PhoneNumber NOT LIKE '415%' AND p.FirstName = 'Gail'
ORDER BY p.LastName;
GO
Here is the result set.
FirstName LastName Phone
---------------------- -------------------- -------------------
Gail Alexander 1 (11) 500 555-0120
Gail Butler 1 (11) 500 555-0191
Gail Erickson 834-555-0132
Gail Erickson 849-555-0139
Gail Griffin 450-555-0171
Gail Moore 155-555-0169
Gail Russell 334-555-0170
Gail Westover 305-555-0100
(8 row(s) affected)
C. Using the ESCAPE clause
The following example uses the ESCAPE clause and the escape character to find the exact character string 10-15% in column c1 of the mytbl2 table.
USE tempdb;
GO
IF EXISTS(SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME = 'mytbl2')
DROP TABLE mytbl2;
GO
USE tempdb;
GO
CREATE TABLE mytbl2
(
c1 sysname
);
GO
INSERT mytbl2 VALUES ('Discount is 10-15% off'), ('Discount is .10-.15 off');
GO
SELECT c1
FROM mytbl2
WHERE c1 LIKE '%10-15!% off%' ESCAPE '!';
GO
D. Using the [ ] wildcard characters
The following example finds employees on the Person table with the first name of Cheryl or Sheryl.
USE AdventureWorks2012;
GO
SELECT BusinessEntityID, FirstName, LastName
FROM Person.Person
WHERE FirstName LIKE '[CS]heryl';
GO
The following example finds the rows for employees in the Person table with last names of Zheng or Zhang.
USE AdventureWorks2012;
GO
SELECT LastName, FirstName
FROM Person.Person
WHERE LastName LIKE 'Zh[ae]ng'
ORDER BY LastName ASC, FirstName ASC;
GO