SELECT ceiling(AVG((salary) - CAST(REPLACE(CAST(salary AS VARCHAR), '0', '') AS Numeric))) FROM Employees;

select ceil(avg(salary)- avg(replace(salary,'0',''))) from employees;

SELECT CEILING(AVG(sal.actual - sal.fake)) AS blunder FROM ( SELECT CEILING(SALARY) AS actual, ROUND(CEILING(CAST(REPLACE(SALARY, '0', '') AS UNSIGNED))) AS fake FROM EMPLOYEES ) AS sal;

MS SQL

SELECT
    CAST(CEILING((Sub.ActualAVG - Sub.FalseAVG)) AS INT) AS DIFFERENCE
FROM
(
    SELECT
        ROUND(AVG(CAST(SALARY AS FLOAT)), 2) AS ActualAVG
    ,   ROUND(AVG(CAST(REPLACE(SALARY, 0, '') AS FLOAT)), 2) AS FalseAVG
    FROM
        EMPLOYEES
) AS Sub

SELECT CEIL(AVG(SALARY) - AVG(REPLACE(SALARY,0,''))) FROM EMPLOYEES;