SQL - STRING_AGG() Function

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The SQL STRING_AGG() function is an aggregate function that is used to concatenate the string values.

It accepts two parameters str and separator concatenates the values of string expressions and places separator values between them. It returns a new concatenated string with the specified separator.

The return type depends on the first argument (string expression), if the expression type is a string, then the result type will be the same as the string expression type.

Note − The separator is not added at the end of the string.

Following is the syntax of the SQL STRING_AGG() function −

STRING_AGG ( exp, separator) [ <order_clause> ])

Parameters

• exp − It is an expression of any type.

• separator − It is an expression of the varchar or nvarchar type, that is used as a separator for concatenated strings.

• <order_clause> − It specifies the sort order of concatenated results using within GROUP clause.

Example

In the following example,we are using the SQL STRING_AGG() function to concatenate the rows of content in single fields.

Assume we have created a table with the name Customers, and if two or more customers have the same ID, we can concatenate the customer's data(like their name, salary, address, etc.) in a single fields with the specified separator GROUP by the column name ID.

Following is the CREATE statement to create the table with the name Customers −

CREATE TABLE CUSTOMERS(    
ID INT NOT NULL,    
FIRST_NAME VARCHAR (20),
LAST_NAME VARCHAR(20),s
AGE INT NOT NULL,    
ADDRESS CHAR (25) ,    
SALARY DECIMAL (18, 2));

Now, let's insert some customer records which having the same ID using the INSERT statement as follows −

INSERT INTO CUSTOMERS VALUES (1, 'Dinesh','Verma', 33, 'Hyderbad', 2200.00 ); 
INSERT INTO CUSTOMERS VALUES (1, 'Ganesh','Kumar', 30, 'Lucknow', 2900.00 ); 
INSERT INTO CUSTOMERS VALUES (1, 'Reeta','Sharma', 23, 'Delhi', 3100.00 ); 

The following SQL query will concatenate the rows which customers having the same ID in the Customers table −

SELECT ID, STRING_AGG(FIRST_NAME,';') All_customer_with_same_Id FROM CUSTOMERS GROUP BY ID;

Output

Following is the output of the above query −

+----+----------------------------+ 
| ID | All_customer_with_same_Id  |  
+----+----------------------------+ 
|  1 | Dinesh;Ganhesh;Reeta;Gane  |   
|  2 | Ramesh                     |  
|  3 | Khilan;kaushik             |  
|  4 | Chaitali                   |  
+----+----------------------------+ 

Example

Following is the another example of the STRING_AGG() function, here we are concatenating the content of the column FIRST_NAME group by the column LAST_NAME.

SELECT STRING_AGG(FIRST_NAME, '/') NEW_LIST FROM CUSTOMERS GROUP BY LAST_NAME;

Output

Following is the output of the above SQL query −

+-----------------+ 
| NEW_LIST        |  
+-----------------+ 
| kaushik/Ganhesh |   
| Ganesh/Ramesh   |  
| Chaitali        |  
| Reeta           |
| Dinesh/Khilan   |  
+-----------------+