mysql 截取某一个时间(datetime类型)的日期：

方法1：select date(row_name) from table_name where row = row1;

方法2：select left(row_name, 10) from table_name where row = row1;

方法3：select cast(row_name as char[10]) from table_name where row = row1;

取得某个日期的time_t数值：select unix_timestamp(date(row_name)) from table_name where row = row1;

以time_t为参数取得某个时间

time_t 是'1970-01-01 00:00:00'以来的秒数

select '1970-01-01 00:00:00'+ INTERVAL time_t_num SECOND ;

取得当前日期：select curdate();

取得当前时间：select now();

将日期转化为短日期格式

SELECT REPLACE(date(row_name),  '-0',  '-');

linux下c++常用时间处理函数

clock()用来程序计时

例如： 以下摘自

#include “stdio.h”

#include “stdlib.h”

#include “time.h”

int main( void )

{

long    i = 10000000L;

clock_t start, finish;

double  duration;

/* 测量一个事件持续的时间*/

printf( "Time to do %ld empty loops is ", i );

start = clock();

while( i-- )      ;

finish = clock();

duration = (double)(finish - start) / CLOCKS_PER_SEC;

printf( "%f seconds\n", duration );

system("pause");

}

示例出处：DIY部落(http://www.diybl.com/course/3_program/vc/vc_js/20090307/159296.html)

time_t类型

time_t  t = time(NULL);

time_t转成tm类型

struct tm*  t_tm = localtime(time(NULL));

time_t转成字符串格式

struct tm* tm_ago = localtime(&t);

sprintf(date_days_ago, "%04d-%02d-%02d", 1900+tm_ago->tm_year,

tm_ago->tm_mon+1, tm_ago->tm_mday);

time_t t_now = time(NULL);   //seconds since 1970-01-01

struct