please fast sql virus problem introduced code in DB delete it

A virus has introduced code into my SQL Database, at least in one table. The table has its original content, but then it has added the following code:

</a><a href='http://tests4all.org/3/'>free quit smoking tool</a> ... etc ...

The original content of that could be something like:

0certifications are accredited</a><a href='http://tests4all.org/3/'>free quit smoking tool</a><a href='http://tests4all.org/4/'>the bluest eyes in texas paraody</a><a href='http://tests4all.org/5/'>sayings cheated off the rode</a><artner parts</a><a href='
 
How can I run an sql in that table ('activities' table)  to delete all the text that its after the </a><a href='http://tests4all.org/3/'>  code, including that code ?  

I as you can imagine this is VERY urgent, also, how can i search for this code in all the other tables of my database without having to go table by table opening them up ?

Later the bigger problem will be to do something to cleanup if there is a virus and prevent this from happening again.