CONCAT function returns the string that results from concatenating the arguments.


Example 1:
SELECT CONCAT(column1,column2) from table;
The output for the above will be
Mohanlal
SureshGopi


In between the two columns if you want space or comma, rewrite the query as below


SELECT CONCAT(column1,',',column2) from table;
The output for the above will be
Mohan,lal
Suresh,Gopi


We can also update the table using CONCAT function.


Example 2:
UPDATE table SET column1=CONCAT(column1,column2)


Example 3:
UPDATE table SET column1=CONCAT(column1,'some string')


Example 4: using PHP
mysql_query("UPDATE table SET column1=CONCAT(column1,' ".$variable." ')");