update the tables sql,asp.net c#

Question

hi, i have two table t1,t2 and one target table t3
 
t1 have 3 columns
t2 have 3 columns (different columns)

i inserted t1,t2 tables and stored successfully
  now i want to copy(column values) the all t1,t2 values in t3 table based on (t1.id=t2.id )

and next i want to fetch all  t3 column values in a gridview
 plz help