mysql cast方法

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Db('study_report_day_info_sp')->field('id,rel_id, max(CAST(video_length as SIGNED))  as m')             ->where('type',$type)             ->where('coid',$coid)             ->where('user_id',$user_id)             ->group('rel_id')             ->order('video_length desc')             ->select();

　　

CAST 和 CONVERT 两个函数中的 type取值可以为：SIGNED，UNSIGNED， DECIMAL，DATE，TIME， DTAETIME等

 

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Db('course')->connect('rongyue')                 ->field('couid, TIME_TO_SEC(duration) as c')                 ->where(['coid' => $coid])                 ->select();

　　

SEC_TO_TIME(second)   秒换算成时分秒

TIME_TO_SEC(date)  时分秒换算成秒