Is possible to reuse a already calculatesd column into a query in MySQL?
You can use user-defined variable.

SELECT @temp := ( /* Complex query */ ) AS myValue, 
       IF ( @temp &gt; 10, "OK" , "" )
FROM table;


Maybe server demands preliminary variable definition. If so,

SELECT @temp := ( /* Complex query */ ) AS myValue, 
       IF ( @temp &gt; 10, "OK" , "" )
FROM table, (SELECT @temp := 0) dummy;


The documentation do not specified the order of output values calculations, but in practice it always matched the order they are written.