


A summary of how php randomly picks mysql records, a summary of phpmysql records
The example in this article summarizes the method of randomly picking mysql records in PHP. Share it with everyone for your reference. The specific analysis is as follows:
To randomly fetch mysql records in php, we can directly use mysql_query to execute the data obtained by the select rand function in mysql and read it out. Here is a brief introduction to you.
Method 1, the code is as follows:
Change the value after limit to the number of items you want to randomly select. Only one is taken here.
Method 2, the code is as follows:
....
$max_num = $row['count']; // Get the total number of records
srand((double)microtime()*1000000); // Random number seed
$se_pos = rand(0, $max_num); // Random number range
$length = 6; // Number of records
if (($max_num - $se_pos) $se_pos = $max_num - $se_pos; // When the number of records is less than 6
}
$query = "SELECT * FROM recommendsn limit ".$se_pos.",".$length;
Example 3, assuming there is a database named xyj, there is a table obj in the database, and a field in the table is name. Now we want to randomly select a record from the table. The specific procedure is as follows:
mysql_select_db("xyj",$db);
$result=mysql_query("SELECT * FROM obj",$db);
$max_num=mysql_num_rows($result);//Get the number of records in the database
srand((double)microtime()*10000000); //Generate random number seed.
$se_pos=rand(0, $max_num-1); //Take a random number from 0 to the maximum number of records
$length=30; //Set how many records to fetch in total
//The following is to retrieve the specified number of records.
$result_lim=mysql_query("select * from obj limit $se_pos,$length",$db);
$myrow_lim=mysql_fetch_array($result_lim);
printf("%sn", $se_pos);//Display the randomly obtained record number
printf("%sn", $myrow_lim["name"]);//Display the name field of the randomly obtained record
?>
I hope this article will be helpful to everyone’s PHP programming design.

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

在PHP中,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。


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