Question

我遇到了问题，我是mysql的初学者，我被分配创建一个从url地址中提取值的查询。所以基本上我有成千上万个这样的网址，例如https://www.google.com/search?source=，我需要提取最后一个＆＃39; /＆＃39;直到第一个＆＃39;（在这种情况下＆＃39;搜索＆＃39;）。并不是那么简单，有时它的http，有时是＆＃39; /＆＃39;字符是不一样的，有时是一个错误的地址（我需要忽略这些情况），有时我有一个案例，我有一个常规的https://google.com/search而没有＆＃39;？＆＃39;（这些情况需要也被忽略了。我在这里，但我感到无助，有什么建议吗？

select distinct SUBSTRING_INDEX(col,'/',0) col from table where length(col) - length(replace(col, '/', '')) >= 1 
         and length(col) - length(replace(col, '?', '')) >= 1 
                and col = 'value'
                    and col <> ''
                      and col is not null 
                        order by date
                         limit 600;

Answer 1

首先测试问号。然后，如果存在使用子串到该位置，反转，找到“斜线之前的？”，然后我可以提取该部分的URL一旦我知道/是和？是：

select
  url
, substr(url,1,qmarkpos-1)
, case when qmarkpos > 0 then instr(reverse(substr(url,1,qmarkpos-1)),'/') end
, substr(substr(url,1,qmarkpos-1),qmarkpos-instr(reverse(substr(url,1,qmarkpos-1)),'/'),qmarkpos)
from (
        select url, instr(url,'?') qmarkpos
        from (
             select 'https://www.google.com/search?source=' as url union all
             select 'https://www.google.com/search' as url union all
             select 'https://www.google.com/search?source=uqu iqu iugqidug iqugd' as url union all
             select 'https://www.google.com/search?source/qh ohqod hi=' as url            
            ) d
     ) d2

+---+-------------------------------------------------------------+-------------------------------+--------------+---------+
|   |                             url                             |   substr(url,1,qmarkpos-1)    | case ... end | result  |
+---+-------------------------------------------------------------+-------------------------------+--------------+---------+
| 1 | https://www.google.com/search?source=                       | https://www.google.com/search | 7            | /search |
| 2 | https://www.google.com/search                               |                               | NULL         |         |
| 3 | https://www.google.com/search?source=uqu iqu iugqidug iqugd | https://www.google.com/search | 7            | /search |
| 4 | https://www.google.com/search?source/qh ohqod hi=           | https://www.google.com/search | 7            | /search |
+---+-------------------------------------------------------------+-------------------------------+--------------+---------+

Demo

只有在符合条件的情况下才能从特定字符中选择特定字符？

1 个答案: