Table check for ip matches

[EchoFool]

Hey im not entirely sure what kind of query im looking for with this...

 

But i have a table with ips linked with userid ... so 1 userid could have many ips obviously.

 

Now say id 1 and id 2 want to make a transaction i want to prevent it by checking this ip table to see if they have ever had an ip that was the same.... =/

 

 

Any ideas what kind of query im looking for mainly related to the WHERE clause ?

[Ken2k7]

SELECT COUNT(*) c
FROM ip_table i1
INNER JOIN ip_table i2
     ON i1.ip = i2.ip
LIMIT 1

 

Not tested, but even if it doesn't work, does it give you an idea how this would be handled?

[EchoFool]

umm i dont understand the COUNT(*) c

 

then the i1 and i2 ? What are they?

[Ken2k7]

They are aliases.

[EchoFool]

They are confusing me as to which are aliases and which are fields in your example :S

[EchoFool]

Would this be correct?

 

SELECT IP 
FROM iplogs t1
   INNER JOIN iplogs t2
   ON t1.IP = t2.IP 
WHERE t1.userID='$UserID1' AND t2.UserID='$UserID2' 
LIMIT 1