MySQL:

CONCAT

Syntax:
CONCAT(str1,str2,...)

Returns the string that results from concatenating the arguments. May
have one or more arguments. If all arguments are nonbinary strings, the
result is a nonbinary string. If the arguments include any binary
strings, the result is a binary string. A numeric argument is converted
to its equivalent nonbinary string form.

CONCAT() returns NULL if any argument is NULL.

URL: https://dev.mysql.com/doc/refman/8.0/en/string-functions.html

Example

mysql> SELECT CONCAT('My', 'S', 'QL');
-> 'MySQL'
mysql> SELECT CONCAT('My', NULL, 'QL');
-> NULL
mysql> SELECT CONCAT(14.3);
-> '14.3'