查询时间间隔：
DATE(create_time) < DATE_SUB(CURDATE(), INTERVAL 1 DAY);
DATE(create_time) < DATE_SUB(CURDATE(), INTERVAL 7 month);
createtime < DATE_SUB(NOW(),INTERVAL 5 MONTH)
根据时间分类排序：
/*按天统计*/
GROUP BY DATE(create_time) ORDER BY DATE(create_time) DESC;
/*按周统计*/
GROUP BY WEEK(create_time) ORDER BY WEEK(create_time) DESC;
/*按月统计*/
GROUP BY MONTH(create_time) ORDER BY MONTH(create_time) DESC;
/*按季度统计*/
GROUP BY QUARTER(create_time) ORDER BY QUARTER(create_time) DESC;
/*按年统计*/
GROUP BY YEAR(create_time) ORDER BY YEAR(create_time) DESC;
/*查年示例写法*/
YEAR(createtime) YEAR
只查询年、月、日、小时、分钟或者组合查询：
格式:EXTRACT(unit FROM date)
unit支持的格式如下：
MICROSECOND,
SECOND,
MINUTE,
HOUR,
DAY,
WEEK,
MONTH,
QUARTER,
YEAR,
DAY_MICROSECOND,
HOUR_MICROSECOND,
MINUTE_MICROSECOND,
SECOND_MICROSECOND,
DAY_HOUR,
DAY_MINUTE,
HOUR_MINUTE,
DAY_SECOND,
HOUR_SECOND,
MINUTE_SECOND,
YEAR_MONTH
获取当前时间
yyyy-mm-dd hh:mm:ss - now()
yyyy-mm-dd hh:mm:ss - curdate()
yyyy-mm-dd hh:mm:ss - curtime()
按小时分组查询
GROUP BY DATE_FORMAT( CREATETIME, \'%Y-%m-%d %H\' )
日期相减计算天数
TO_DAYS(日期)-TO_DAYS(日期)
