Hack attempt on my Blog – Advice needed

Just been looking at Counterize log and found that someone had used the search function on my blog to search for this :

�’)))/**/AND/**/ID=-1/**/UNION/**/SELECT/**/1,2,0x3a,user_login,0x3a,user_pass,0x3a,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24/**/FROM/**/wp_users#

Now seeing as this search string has the word “user_login” and “user_pass” included in it, I suspect this was an attempt to get login details for my wordpress installation, wondered if anyone else had come across this and is there a need to worry as obviously I don’t know if they managed to get the information they were after.

Thxs in advance