mysql 将字段time按天/月/年分组
假设表中有一个字段time,格式为Unix时间戳，现需要按照该字段统计每天的记录数。 方法： 利用convert函数convert(char(10),time,120) as time，然后group by time即可。 原理：convert函数将时间戳转换成ODBC标准时间(120参数指定)，然后取前十位，则刚好得
假设表中有一个字段time,格式为Unix时间戳，现需要按照该字段统计每天的记录数。
方法：
利用convert函数convert(char(10),time,120) as time，然后group by time即可。
原理：convert函数将时间戳转换成ODBC标准时间(120参数指定)，然后取前十位，则刚好得到完整日期(不含时分秒)，再分组即可。
按月，按年分组方法一样，只需要修改convert()方法第一个参数的长度。
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