MySQL CONCAT() is MySQL defined Function .
MySQL CONCAT() function is usefull to combine any number of strings in MySQL .
for example
select CONCAT('One ' , '1 ', "Two ", '2')
above select query with CONCAT will return one string combined of all passed strings.
so output
One 1 Two 2
so you can say syntax of the MySQL CONCAT() function is :
CONCAT(string1, string2,string3 .... )
here CONCAT function's parameters can be fieldnames or strings
for example three field firstname , middlename and lastname combined as full name by MySQL CONCAT() function:
select CONCAT(firstname," ",middlename," ",lastname) as name