Szerkesztés

Megosztás a következőn keresztül:

CONCAT (Transact-SQL)

  • Cikk

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) SQL analytics endpoint in Microsoft Fabric Warehouse in Microsoft Fabric

This function returns a string resulting from the concatenation, or joining, of two or more string values in an end-to-end manner.

Note

To add a separating value during concatenation, use CONCAT_WS.

Transact-SQL syntax conventions

Syntax

CONCAT ( argument1 , argument2 [ , argumentN ] ... )

Arguments

argument1, argument2 [ , argumentN ]

An expression of any string value. The CONCAT function requires at least two arguments, and no more than 254 arguments.

Return types

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 raises 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 returns an empty string of type varchar(1). The implicit conversion to strings follows the existing rules for data type conversions. For more information about data type conversions, see CAST and CONVERT (Transact-SQL).

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 up to 4000 characters (nvarchar(<= 4000)) nvarchar(<= 4000)
4. In all other cases any argument of type varchar of up to 8000 characters (varchar(<= 8000)), 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 with value 14 has a string length of 2, while a float with value 1234.56789 has a string length of 7 (1234.57). Therefore, a concatenation of these two values returns a result with a length of no less than 9 characters.

If none of the input arguments has a supported large object (LOB) type, then the return type truncates to 8,000 characters in length, regardless of the return type. This truncation preserves space and supports plan generation efficiency.

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

Examples

A. Use CONCAT

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

Here's the result set.

Result
--------------------
Happy Birthday 11/25

B. Use 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;

Here's the result set.

Result
------------
NameLastname

Related content