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CONCAT_WS (Transact-SQL)

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Applies to: SQL Server 2017 (14.x) and later Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics 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. It separates those concatenated string values with the delimiter specified in the first function argument. (CONCAT_WS indicates concatenate with separator.)

Syntax

syntaxsql 
CONCAT_WS ( separator , argument1 , argument2 [ , argumentN ] ... )

Arguments

separator

An expression of any character type (char, nchar, nvarchar, or varchar).

argument1, argument2 [ , argumentN ]

An expression of any string value. The CONCAT_WS 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_WS takes a variable number of string arguments and concatenates (or joins) them into a single string. It separates those concatenated string values with the delimiter specified in the first function argument. CONCAT_WS requires a separator argument and a minimum of two other string value arguments; otherwise, CONCAT_WS raises an error. CONCAT_WS implicitly converts all arguments to string types before concatenation.

The implicit conversion to strings follows the existing rules for data type conversions. For more information about behavior and data type conversions, see CONCAT (Transact-SQL).

Treatment of NULL values

CONCAT_WS ignores the SET CONCAT_NULL_YIELDS_NULL { ON | OFF } setting.

If CONCAT_WS receives arguments with all NULL values, it returns an empty string of type varchar(1).

CONCAT_WS ignores null values during concatenation, and doesn't add the separator between null values. Therefore, CONCAT_WS can cleanly handle concatenation of strings that might have "blank" values - for example, a second address field. For more information, see Example B.

If a scenario involves null values separated by a delimiter, consider the ISNULL function. For more information, see Example C.

Examples

A. Concatenate values with separator

This example concatenates three columns from the sys.databases table, separating the values with a hyphen surrounded by spaces (-).

SQL 
SELECT CONCAT_WS(' - ', database_id, recovery_model_desc, containment_desc) AS DatabaseInfo
FROM sys.databases;

Here's the result set.

Output 
DatabaseInfo
-----------------
1 - SIMPLE - NONE
2 - SIMPLE - NONE
3 - FULL - NONE
4 - SIMPLE - NONE

B. Skip NULL values

This example ignores NULL values in the arguments list, and uses a comma separator value (,).

SQL 
SELECT CONCAT_WS(',', '1 Microsoft Way', NULL, NULL, 'Redmond', 'WA', 98052) AS Address;

Here's the result set.

Output 
Address
--------------------------------
1 Microsoft Way,Redmond,WA,98052

C. Generate CSV-formatted data from table

This example uses a comma separator value (,), and adds the carriage return character CHAR(13) in the comma-separated values format of the result set.

SQL 
SELECT STRING_AGG(
    CONCAT_WS(',', database_id, recovery_model_desc, containment_desc), CHAR(13)
) AS DatabaseInfo
FROM sys.databases;

Here's the result set.

Output 
DatabaseInfo
-------------
1,SIMPLE,NONE
2,SIMPLE,NONE
3,FULL,NONE
4,SIMPLE,NONE

CONCAT_WS ignores NULL values in the columns. Wrap a nullable column with the ISNULL function, and provide a default value. For example:

SQL 
SELECT STRING_AGG(
    CONCAT_WS(',', database_id, ISNULL(recovery_model_desc, ''), ISNULL(containment_desc, 'N/A')), CHAR(13)
) AS DatabaseInfo
FROM sys.databases;

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