在mysql里怎么查找最后数天的数据？

mysql>select * from (select a1.othercol,a1.Datecol,a2.lastdate from yourtable as a1 join (select max(Datecol) as lastdate from yourtable) as a2) where datediff(lastdate,Datecole)<30

上方othercol指其他列，Datecol指日期列，yourtable是你的table名称，将30换成你需要的天数

如果是SQLSERVER Or Access

select * from tab where isnumeric(name)<>0

如果ORACLE ，由于Oracle没有自带的判断数字的函数，需要自创建函数isnumeric

　CREATE OR REPLACE FUNCTION isnumeric (str IN VARCHAR2)

RETURN NUMBER

IS

v_str FLOAT

BEGIN

IF str IS NULL

THEN

RETURN 0

ELSE

BEGIN

SELECT TO_NUMBER (str)

INTO v_str

FROM DUAL

EXCEPTION

WHEN INVALID_NUMBER

THEN

RETURN 0

END

RETURN 1

END IF

END isnumeric

用法：

select * from tab where isnumeric(name)<>0

select * from student limit 5

select * from student limit 0,5

select * from student order by id asc limit 5

前五条记录的查询语句。

查询后5条，注意结果为倒序排序，要使用desc

select * from student order by id desc limit 5

select * from student limit m,n

返回m+1到m+n行记录,m代表开始的下标，n代表查找的结果数，将返回n行结果

select * from student limit 2,8返回3到10行记录

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