Create Table... as Select * from..... Vs Insert into table.....Select * from .....

Question

Hi All,
I am having one query as below:
There is a master table named: MSTR_TABLE  (It's having partitions on a month column [YYYYMM] )
I am having 4 temp Tables As: Temp1, Temp2, temp3, Temp4 (These tables are not having any index, no partitions)
Scenario 1: I am trying to insert data into MSTR_TABLE from Temp1, Temp2, temp3, Temp4 tables (Select data from temp tables by Outer Join), which i taking lot's of time. Coming to no of records in temp tables are Temp1: 5 Million Records,
                       Temp2: 3 Million Records,
                       Temp3: 0.5 Million records,
                       Temp4: 5000 Records
Scenario 2: Creating a new Table as TEMP_MASTER using Temp1, Temp2, temp3, Temp4 tables. This is executing much faster and the table is getting created in less than 10 mins.
Scenario 3: Now i am inserting data from TEMP_MASTER to MSTR_TABLE. This is is also getting executed in less than 5 mins.
I tried following methods:
1) Creating a table with partitions and tried Inserting Data - No Luck
2) Disabled Logging on table and tried Inserting data - No Luck
3) used /*+ append nologging*/ and tried inserting data - No Luck
4) Altered Next Extent to 8MB and tried - No Luck
Please let me know, why while inserting into main table (Scenario 1) from query is not working and running long time (More than 2 hrs).
Thanks in Advance,
Venu Gopal K

Answer 1

Hi Sudhakar,
Thanks for your reply. Please find the detailed description of situation as below:
MSTR_TABLE: Existing Number of columns : 120
                        Indexes: NO
                        Partitions: On Month Column (Datatype: Number, format (YYYYMM, Ex: 201205))
                        Inserting Data for every month
I added 18 new columns to MSTR_TABLE and the requirement is to populate data for 18 columns. These 18 columns data i am fetching from multiple tables and storing in temp tables as below, and creating a new table by joining PRNT_TABLE, TEMP1,TEMP2,TEMP3,TEMP4 and fetching 120+18 columns data and storing in MSTR_TABLE.
PRNT_TABLE:  Existing Number of columns : 120
                        Indexes: NO
                        Partitions: On Month Column (Datatype: Number, format (YYYYMM, Ex: 201205))
                        Data : more than 100 Million records
TEMP1: No Index, No Partitions (No Of Rows: 5 million)
TEMP2: No Index, No Partitions  (No Of Rows: 4 million)
TEMP3: No Index, No Partitions  (No Of Rows: 30000)
TEMP4: No Index, No Partitions  (No Of Rows: 5000)
Queries are as follows:
Scenario 1:
Insert into MSTR_TABLE
(col1,
col2,
col3,
col119,
col120,
New_col121,
New_col122,
New_col138)
select col1, col2, col3 ...............col119, col120, New_col121, New_col122.................New_col138
from PRNT_TABLE, TEMP1,TEMP2,TEMP3,TEMP4
where PRNT_TABLE.Col1 = TEMP1.Col1(+)
   AND PRNT_TABLE.Col1 = TEMP1.Col1(+)
   AND PRNT_TABLE.Col1 = TEMP1.Col1(+)
  AND PRNT_TABLE.Col1 = TEMP1.Col1(+)
   AND  PRNT_TABLE.Month  = 201102
Execution Plan Statistics: INSERT STATEMENT  ALL_ROWSCost: 19,451,465  Bytes: 2,472,327,442  Cardinality: 5,593,501 
Scenario 1:
Create table NEW_TABLE
as
select col1, col2, col3 ...............col119, col120, New_col121, New_col122.................New_col138
from PRNT_TABLE, TEMP1,TEMP2,TEMP3,TEMP4
where PRNT_TABLE.Col1 = TEMP1.Col1(+)
   AND PRNT_TABLE.Col1 = TEMP1.Col1(+)
   AND PRNT_TABLE.Col1 = TEMP1.Col1(+)
  AND PRNT_TABLE.Col1 = TEMP1.Col1(+)
   AND  PRNT_TABLE.Month  = 201102
Execution Plan Statistics: CREATE TABLE STATEMENT  ALL_ROWSCost: 19,500,277  Bytes: 2,472,327,442  Cardinality: 5,593,501 
Thanks,
Venu Gopal K.