倒向类语句

Posted 2021-02-27

Sometimes you need TO think backwards.
 
Here was the problem. I needed TO MATCH up SOME IP address ranges TO the company that owns them. Looking FOR a simple solution TO the problem I came up WITH storing the IP address block patterns IN the DATABASE AS follows:
 
ip_pattern
----------------
127.%.%.%
192.168.%.%
10.%.%.%
 
Any idea why I choose % AS the wildcard?
 
That's right - it's the wildcard operator IN SQL FOR the LIKE statement.
 
So now WHEN I have have an IP address 192.168.1.1, I can do what I LIKE TO CALL a backwards LIKE query:
 
SELECT company, ip_pattern
FROM company_blocks
WHERE '192.168.1.1' LIKE ip_pattern
 
This works ON SQL Server AND mysql, AND I would think it should WORK fine ON any DATABASE server.