


1. For example, the format of a field in the table is as follows: data 1|||||data 2|||||data 3
2. Now I want to split the data into $data[0],$data[1],$ data[3], and then order by $data[3]
3. Can this be achieved?
4. A complete novice, the description may not be standardized, but the meaning should be clear.
Reply content:
1. For example, the format of a field in the table is as follows: data 1|||||data 2|||||data 3
2. Now I want to split the data into $data[0],$data[1],$ data[3], and then order by $data[3]
3. Can this be achieved?
4. A complete novice, the description may not be standardized, but the meaning should be clear.
It can be implemented, but if implemented at the MySQL level, it may cause greater pressure on the database.
You can consider sorting it in the PHP program, and then fetching the data from MySQL based on the ID sequence.
<code><?php header('Content-Type: text/plain; charset=utf-8'); //$db = new mysqli('127.0.0.1','user','pass','dbname',3306); //$arr = $db->query('SELECT id,field FROM table')->fetch_all(MYSQLI_ASSOC); //假设取出来的数据结构如下 $arr = array( array('id' => 1, 'field' => '数据1|||||数据2|||||256'), array('id' => 2, 'field' => '数据1|||||数据2|||||128'), array('id' => 3, 'field' => '数据1|||||数据2|||||512'), ); foreach($arr as $k => $v) { //把field字段的内容转成一个数组比如array('数据1','数据2','256'),方便后面排序 $arr[$k]['field'] = explode('|||||', $v['field']); } //根据field字段里的第三个元素对数组进行排序 uasort($arr, function($a, $b) { if($a['field'][2]===$b['field'][2]) return 0; //下面这句话的意思就是,如果前面的a大过后面的b,就返回1,返回1表示交换顺序,也就是小的数在前面,由小到大升序排列. else return ($a['field'][2] > $b['field'][2]) ? 1 : -1; }); foreach($arr as $k => $v) { $ids[] = $v['id']; } $ids = implode(',', $ids); //ID序列为2,1,3 //按照ID序列的顺序查询MySQL //SQL语句为 SELECT * FROM table WHERE id IN(2,1,3) ORDER BY FIELD(id,2,1,3) $sql = "SELECT * FROM table WHERE id IN($ids) ORDER BY FIELD(id,$ids)"; //$ret = $db->query($sql)->fetch_all();</code>
If the amount of data is large, you can consider caching the ID sequence arranged by PHP.
ORDER BY FIELD (id, $ids) This operation will also cause performance problems when the amount of data is large.
At this time, you can consider caching the ID sequence based on the actual situation. Segment $ids, for example, sort 20 items from 0 to 19 on the first page, and so on on the second page. In this way, custom sorting of small data amounts will put much less pressure on MySQL.
This has nothing to do with php. You can create a function with mysql and then use the function to sort:
<code>CREATE FUNCTION SPLIT_STRING(str VARCHAR(255), delim VARCHAR(12), pos INT) RETURNS VARCHAR(255) RETURN REPLACE(SUBSTRING(SUBSTRING_INDEX(str, delim, pos), LENGTH(SUBSTRING_INDEX(str, delim, pos-1)) + 1), delim, '');</code>
<code>SELECT * FROM test_table order by SPLIT_STRING(test_tablecol, '|||', 3);</code>
It can be implemented, but it is very troublesome and very inefficient. The usual solution to this requirement is to modify the table structure.
From a purely logical point of view, SQL can actually do very complex things, but do you think if a query takes several minutes to run and your family members find out, will you be beaten?
It is recommended to use php to sort after querying, not mysql
substring_index of mysql

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。

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。

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)”。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


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