MySQL CONCAT() Function

In MySQL, the CONCAT() function is used to join two or more specified strings in order and return the result. If you need to join multiple strings with delimiters, please use the CONCAT_WS() function.

The CONCAT() function returns NULL if one of the arguments is NULL.

CONCAT() Syntax

Here is the syntax of MySQL CONCAT() function:

CONCAT(string1, string2, ..., stringN)

Parameters

string1, string2, ..., stringN

Required. You must specify at least one string. If one of the parameters is NULL, MySQL CONCAT() function will be returned NULL; If no string is specified, MySQL CONCAT() function will report an error: ERROR 1582 (42000): Incorrect parameter count in the call to native function 'CONCAT'.

Return value

The CONCAT() function returns the joined string.

• The CONCAT() function will return NULL if one of the arguments is NULL.
• If there is only one parameter, the CONCAT() function will return the parameter itself.

CONCAT() Example

• To join the strings 'Hello' and 'World', use the following statement:

  SELECT CONCAT('Hello', 'World');
  

  +--------------------------+
  | CONCAT('Hello', 'World') |
  +--------------------------+
  | HelloWorld               |
  +--------------------------+

  Note that the CONCAT() function doesn’t add a delimiter to the concatenated string, so the result is 'HelloWorld'. If you want to separate with spaces, use the following statement:

  SELECT CONCAT('Hello', ' ', 'World');
  

  +-------------------------------+
  | CONCAT('Hello', ' ', 'World') |
  +-------------------------------+
  | Hello World                   |
  +-------------------------------+

• Returns NULL if one of the arguments is NULL. See the example below:

  SELECT CONCAT('Hello', NULL);
  

  +-----------------------+
  | CONCAT('Hello', NULL) |
  +-----------------------+
  | NULL                  |
  +-----------------------+