CAST int
to char
. I hope, it will work.
CREATE TABLE test2 SELECT CONCAT(a,b,CAST(c AS CHAR)) AS d FROM test;
Update:
After Lightness Races in Orbit's comment, I tried it for myself. Usually, it works just fine. But since your version is a bit older one, it is not working.
You can use it like the following way:
CREATE TABLE test2 (d char(9));
INSERT INTO test2
SELECT CONCAT(a,b,c) AS d FROM test;
See the sqlfiddle: http://sqlfiddle.com/#!8/d9433/1