MySQL case when生成新的列

[seaswalker]

SELECT
    (
        case
            when c = 1 then '100%'
            ELSE concat(ROUND((a / b) * 100, 2), '%')
        end
    ) AS '百分比'
FROM
    some_table

如果c不等于1那么得到的是保留两位小数的百分比.