CONCAT (Transact-SQL)

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This function returns a string resulting from the concatenation, or joining, of two or more string values in an end-to-end manner. (To add a separating value during concatenation, see CONCAT_WS.)

Topic link icon Transact-SQL Syntax Conventions

Syntax

CONCAT ( string_value1, string_value2 [, string_valueN ] )

Arguments

string_value
A string value to concatenate to the other values. The CONCAT function requires at least two string_value arguments, and no more than 254 string_value arguments.

Return types

string_value
A string value whose length and type depend on the input.

Remarks

CONCAT takes a variable number of string arguments and concatenates (or joins) them into a single string. It requires a minimum of two input values; otherwise, CONCAT will raise an error. CONCAT implicitly converts all arguments to string types before concatenation. CONCAT implicitly converts null values to empty strings. If CONCAT receives arguments with all NULL values, it will return an empty string of type varchar(1). The implicit conversion to strings follows the existing rules for data type conversions. See CAST and CONVERT (Transact-SQL) for more information about data type conversions.

The return type depends on the type of the arguments. This table illustrates the mapping:

Input type	Output type and length
1. Any argument of a SQL-CLR system type a SQL-CLR UDT or `nvarchar(max)`	nvarchar(max)
2. Otherwise, any argument of type varbinary(max) or varchar(max)	varchar(max), unless one of the parameters is an nvarchar of any length. In this case, `CONCAT` returns a result of type nvarchar(max).
3. Otherwise, any argument of type nvarchar of at most 4000 characters ( nvarchar(<= 4000) )	nvarchar(<= 4000)
4. In all other cases	varchar(<= 8000) (a varchar of at most 8000 characters) unless one of the parameters is an nvarchar of any length. In that case, `CONCAT` returns a result of type nvarchar(max).

When CONCAT receives nvarchar input arguments of length <= 4000 characters, or varchar input arguments of length <= 8000 characters, implicit conversions can affect the length of the result. Other data types have different lengths when implicitly converted to strings. For example, an int (14) has a string length of 12, while a float has a length of 32. Therefore, a concatenation of two integers returns a result with a length of no less than 24.

If none of the input arguments has a supported large object (LOB) type, then the return type truncates to 8000 characters in length, regardless of the return type. This truncation preserves space and supports plan generation efficiency.

The CONCAT function can be executed remotely on a linked server of version SQL Server 2012 (11.x) and above. For older linked servers, the CONCAT operation will happen locally, after the linked server returns the non-concatenated values.

Examples

A. Using CONCAT

SELECT CONCAT ( 'Happy ', 'Birthday ', 11, '/', '25' ) AS Result;

Here is the result set.

Result  
-------------------------  
Happy Birthday 11/25  
  
(1 row(s) affected)

B. Using CONCAT with NULL values

CREATE TABLE #temp (  
    emp_name nvarchar(200) NOT NULL,  
    emp_middlename nvarchar(200) NULL,  
    emp_lastname nvarchar(200) NOT NULL  
);  
INSERT INTO #temp VALUES( 'Name', NULL, 'Lastname' );  
SELECT CONCAT( emp_name, emp_middlename, emp_lastname ) AS Result  
FROM #temp;