分支判断IFNULL()函数

SELECT

            IFNULL(employees.commission_pct,0) as 奖金率,

            employees.commission_pct

FROM

            employees; 

# --------------------------------

SELECT

            CONCAT(employees.first_name,',',employees.last_name,',',employees.job_id,',',IFNULL(employees.commission_pct,0)) as out_put 

FROM

            employees;