title: ORACLE join multiple tables performance
body: <p>I have kinda complex question.
  Let's say that I have 7 tables (20mil+ rows each) (Table1, Table2 ...) with corresponding pk (pk1, pk2, ....) (cardinality among all tables is 1:1)
  I want to get my final table (using hash join) as:</p>
  
  <pre><code>Create table final_table as select   
  t1.column1,  
  t2.column2,  
  t3.column3,  
  t4.column4,  
  t5.column5,  
  t6.column6,  
  t7.column7  
  from table1 t1  
  join table2 t2 on t1.pk1 = t2.pk2  
  join table2 t3 on t1.pk1 = t3.pk3   
  join table2 t4 on t1.pk1 = t4.pk4     
  join table2 t5 on t1.pk1 = t5.pk5  
  join table2 t6 on t1.pk1 = t6.pk6  
  join table2 t7 on t1.pk1 = t7.pk7
  </code></pre>
  
  <p>I would like to know if it would be faster to create partial tables and then final table, like this?</p>
  
  <pre><code>Create table partial_table1 as select   
  t1.column1,  
  t2.column2  
  from table1 t1  
  join table2 t2 on t1.pk1 = t2.pk2
  
  
  
  create table partial_table2 as select   
  t1.column1, t1.column2  
  t3.column3  
  from partial_table1 t1  
  join table3 t3 on t1.pk1 = t3.pk3
  
  
  
  create table partial_table3 as select  
  t1.column1, t1.column2, t1.column3   
  t4.column4   
  from partial_table1 t1   
  join table3 t4 on t1.pk1 = t4.pk4
  
  
  
  ...  
  ...  
  ... 
  </code></pre>
  
  <p>I know it depends on RAM (because I want to use hash join), actual server usage, etc.. I am not looking for specific answer, I am looking for some explanations why and in what situations would it be better to use partial results or why it would it be better to use all 7 joins in 1 select.<br>
  Thanks, I hope that my question is easy to understand.</p>