SQL Problem

I have two tables which have exactly the same structure. Both of them
have one datetime column along with three other columns. But the
datetime column value in the second table is NULL for all the rows. Now
I want select the least date(date with the least value in the datetime
column) from the first table and update all the rows in the second table
with this least date value from the first table. I do not want to use
any compiler or host variables. I should be able to do this only using
SQL statements. Cn somebody please help me? Thanks in advance.

regards
Imtiaz