MySQL Gets or queries a specific few of the database fields

MORE: http://www.webyang.net/Html/web/article_138.html

MySQL is often used to query specific fields, and occasionally need to show a certain part of the value in a particular field, how to deal with it?

Then there are fuzzy queries, if you need to match some part of the value of the middle, this time like is very awkward, will be more irrelevant records, and how to deal with it?

First, get the specific few:
1. Take the three-bit character after the URL field

 
   
  

  
    
   
Select SUBSTRING (url,-3)   from link;
 
   
  

#这种只能针对固定长度, the URL is a total of 8 characters, you can follow this notation

 
   
  

  
    
   
Select  Right (' url',length(' url ')-5) from link ;  
 
   
  

2, starting from the left 3rd place (including the third place)

 
   
  

  
    
   
Select SUBSTRING (url,3)   from link;
 
   
  

3, take the left 3 digits

 
   
  

  
    
   
Select SUBSTRING (url,1,3)   from link;
 
   
  

#这种只能针对固定长度, the URL is a total of 8 characters, you can follow this notation

 
   
  

  
    
   
Select  Left (' url',length(' url ')-5) from link ;  
 
   
  

4, Intermediate intercept (starting from the 1th bit to take 7 bits, such as the Sdate field value is 2013-06-07)

 
   
  

  
    
   
Select SUBSTRING (sdate,1,7)   from forumdata;
 
   
  

The query results are 2013-06.

Second, the query specific several:
1, the normal fuzzy query

 
   
  

  
    
   
Select* from where '%31% ';
 
   
  

2, a field total of 13 bits, query the bottom four or five bits 31

  
 

   
  

  
select    *  Span class= "PLN" > from   Cm_order  where   SUBSTRING   ( ORDERSN     9   2     =    31   
   
  

  
SELECT *     from Cm_order  where  right(' ordersn ',  Length(' ordersn ')-8)  like ' 31% ' ;
  
 

If the normal fuzzy query will come out a lot of irrelevant data, but this only for fixed-length fuzzy query, efficiency than normal fuzzy query much better.

MySQL Gets or queries a specific few of the database fields