String Concatenation Operator
The string concatenation operator is the plus sign (+). You can combine, or concatenate, two or more character strings into a single character string. You can also concatenate binary strings. This is an example of concatenation:
SELECT ('abc' + 'def')
Here is the result set:
------
abcdef
(1 row(s) affected)
This query displays names of authors with California addresses under the Moniker column in last name, first name order, with a comma and space after the last name.
USE Northwind
GO
SELECT LastName + ', ' + FirstName AS Moniker
FROM Employees
WHERE Region = 'WA'
Here is the result set:
Moniker
-------------------------
Davolio, Nancy
Fuller, Andrew
Leverling, Janet
Peacock, Margaret
Callahan, Laura
(15 row(s) affected)
Other data types, such as datetime and smalldatetime, must be converted to character strings using the CAST conversion function before they can be concatenated with a string.
USE pubs
SELECT 'The due date is ' + CAST(pubdate AS varchar(128))
FROM titles
WHERE title_id = 'BU1032'
Here is the result set:
---------------------------------------
The due date is Jun 12 1991 12:00AM
(1 row(s) affected)
The empty string ('') is evaluated as a single space:
SELECT 'abc' + '' + 'def'
Here is the result set:
-------
abcdef
(1 row(s) affected)
Note Whether an empty string ('') is interpreted as a single blank character or as an empty character is determined by the compatibility level setting of sp_dbcmptlevel. For this example, if sp_dbcmptlevel is 65, empty literals are treated as a single blank.
When the input strings both have the same collation, the output string has the same collation as the inputs. When the input strings have different collations, the rules of collation precedence determine the collation of the output string. You can also assign a specific collation using the COLLATE clause.