sqrt()

select sqrt(16); // output is 4
select sqrt(20); // output is 4.47213595499958

select sqrt(-25); // output is NULL

Example of sqrt function with update query

H2 = A2 + B2;

H= Square root of (A2 + B2) ;

update sql_sqrt set H=sqrt(pow(A,2) + pow(B,2))

require 'config.php'; // Database connection
$sql=$dbo->prepare("update sql_sqrt set H=sqrt(pow(A,2) + pow(B,2))");
if($sql->execute()){
echo "Successfully updated H";
}// End of if profile is ok 
else{
print_r($sql->errorInfo()); // if any error is there it will be posted
$msg=" Database problem, please contact site admin ";
}