求助：MySQL计算varchar格式含毫秒时间与最优时间的差值

MySQL中timpi表的timpPS字段为varchar类型，存储选手耗时数据，格式为分钟:秒,毫秒（示例：02:18,1、02:18,10、02:18,325）。需计算每条数据与最优时间（该字段最小值）的差值，用于PHP展示，但最初编写的SQL语句在差值超过1分钟时计算结果错误。

尝试的错误SQL语句 #

SELECT timpPS, 
(str_to_date( TimpPS, '%i:%s,%f' )) AS Timp,
(SELECT min( str_to_date( TimpPS, '%i:%s,%f' )) FROM timpi ) AS minim,
(str_to_date( concat("00:",TimpPS), '%H:%i:%s,%f' ) - (SELECT min( str_to_date( concat("00:",TimpPS), '%H:%i:%s,%f' )) FROM timpi )) AS Diff 
FROM
    timpi 
ORDER BY
    Diff ASC;

测试数据及错误结果 #

最优时间为02:16,0，但差值超过1分钟时（如03:16,0与最优时间的差值应为60秒），错误SQL计算出的Diff结果不符合预期。

正确的SQL语句 #

SELECT timpPS, 
(str_to_date( TimpPS, '%i:%s,%f' )) AS Timp,
(SELECT min( str_to_date( TimpPS, '%i:%s,%f' )) FROM timpi ) AS minim,
TIMEDIFF(str_to_date( TimpPS, '%i:%s,%f' ),(SELECT min( str_to_date( TimpPS, '%i:%s,%f' )) FROM timpi )) AS Diff 
FROM
    timpi 
ORDER BY
    Diff ASC;

内容的提问来源于stack exchange，提问作者Topo_AS