MySQL中的max()函数使用教程
MySQL的max()函数是用来找出一个记录集中的最大值记录。
要了解MAX功能考虑的EMPLOYEE_TBL表具有以下记录:
mysql>SELECT*FROMemployee_tbl; +------+------+------------+--------------------+ |id|name|work_date|daily_typing_pages| +------+------+------------+--------------------+ |1|John|2007-01-24|250| |2|Ram|2007-05-27|220| |3|Jack|2007-05-06|170| |3|Jack|2007-04-06|100| |4|Jill|2007-04-06|220| |5|Zara|2007-06-06|300| |5|Zara|2007-02-06|350| +------+------+------------+--------------------+ 7rowsinset(0.00sec)
现在,假设根据上述要取表中daily_typing_pages的最大值值,简单地使用下面的命令:
mysql>SELECTMAX(daily_typing_pages) ->FROMemployee_tbl; +-------------------------+ |MAX(daily_typing_pages)| +-------------------------+ |350| +-------------------------+ 1rowinset(0.00sec)
可以找到所有的记录,最大值为每名使用GROUPBY子句如下:
mysql>SELECTid,name,work_date,MAX(daily_typing_pages) ->FROMemployee_tblGROUPBYname; +------+------+------------+-------------------------+ |id|name|work_date|MAX(daily_typing_pages)| +------+------+------------+-------------------------+ |3|Jack|2007-05-06|170| |4|Jill|2007-04-06|220| |1|John|2007-01-24|250| |2|Ram|2007-05-27|220| |5|Zara|2007-06-06|350| +------+------+------------+-------------------------+ 5rowsinset(0.00sec)
也可以使用MIN函数及MAX功能找到的最低值,试试下面的例子:
mysql>SELECTMIN(daily_typing_pages)least,MAX(daily_typing_pages)max ->FROMemployee_tbl; +-------+------+ |least|max| +-------+------+ |100|350| +-------+------+ 1rowinset(0.01sec)