select 
  t1.cust_id, t1.col1, t1.col2, 
  t2.col1_table2, t2.col2_table2, 
  t3.col1_table3, t3.col2_table3
from
 table1 t1 
inner join
 table2 t2 on t1.cust_id = t2.cust_id
join table3 t3 on t1.cust_id = t3.cust_id