Copying million of records from one table to another

Question

How to copy million of records from one table to another table. If there is any error occurs while copying the records, i need the records(Errored out records) that should be copied to someother table.

Answer 1

Use the LOG ERRORS feature. It writes row-level failure information out to a previously defined error log table - and keeps on going. Here's a LiveSQL script that takes you through the steps. I also offer them below. It assumes you have access to the employees table, which you can install from here.

One REALLY important thing to keep in mind about LOG ERRORS is that so long as the number of errors encountered is less than the limit (or the limit is "unlimited"), no error is raised after the statement completes.

Hope this helps!

BEGIN  
   DBMS_ERRLOG.create_error_log (dml_table_name => 'EMPLOYEES');  
END; 
/

-- Show Columns of Error Log Table
-- DBMS_ERRLOG creates a table that starts with five error-related columns: ORA_ERR_NUMBER$ (error code), ORA_ERR_MESG$ (error message), ORA_ERR_ROWID$, ORA_ERR_OPTYP$ (operation type - U, I, D), ORA_ERR_TAG$ (optional "tag" text you can provide in LOG ERRORS clause). Then it adds VARCHAR2(4000) columns for any column in DML table that is compatible with VARCHAR2. Example: DATE works, but CLOB does not.
SELECT column_name, data_type 
  FROM user_tab_columns 
 WHERE table_name = 'ERR$_EMPLOYEES' 
ORDER BY COLUMN_ID;

-- All or Nothing - Without LOG ERRORS
-- This step shows you how the results of a DML statement are usually "all or nothing" - either all rows specified by the DML statement are changed successfully, or none are. That is, if N rows are modified, but then the N+1 row causes an error, the changes to the previous N rows are rolled back. So the number of people making a salary > 24000 is 0, both before and after the UPDATE, since at least one person's salary, when multiplied by 200, exceeds the constraint on the salary column.
DECLARE  
   l_count   PLS_INTEGER;  
BEGIN  
   SELECT COUNT ( * )  
     INTO l_count  
     FROM employees  
    WHERE salary > 24000;  

   DBMS_OUTPUT.put_line ('Before ' || l_count);  

   UPDATE employees  
      SET salary = salary * 200;  

   SELECT COUNT ( * )  
     INTO l_count  
     FROM employees  
    WHERE salary > 24000;  
EXCEPTION  
   WHEN OTHERS  
   THEN  
      DBMS_OUTPUT.put_line (DBMS_UTILITY.format_error_stack);  

      SELECT COUNT ( * )  
        INTO l_count  
        FROM employees  
       WHERE salary > 24000;  

      DBMS_OUTPUT.put_line ('After ' || l_count);  
END; 
/

-- Suppressing Row-Level Errors
-- Now I run the script again, with LOG ERRORS added, also specifying that I don't care how many errors occur - just keeping going. The net result is that of the 107 rows in the employees table, 49 are updated, while 58 have errors. Nice!
DECLARE  
   l_count   PLS_INTEGER;  
BEGIN  
   SELECT COUNT ( * )  
     INTO l_count  
     FROM employees  
    WHERE salary > 24000;  

   DBMS_OUTPUT.put_line ('Before ' || l_count);  

       UPDATE employees  
          SET salary = salary * 200  
LOG ERRORS  INTO ERR$_EMPLOYEES (substr (last_name, 1, 20)) REJECT LIMIT UNLIMITED;   

   DBMS_OUTPUT.put_line ('After - SQL%ROWCOUNT ' || SQL%ROWCOUNT);   

   SELECT COUNT ( * )   
     INTO l_count   
     FROM employees   
    WHERE salary > 24000;   

   DBMS_OUTPUT.put_line ('After - Count in Table ' || l_count);  

   ROLLBACK;  
END; 
/

SELECT COUNT ( * ) "Number of Failures" 
  FROM err$_employees ;

-- Check the Error Log Table!
-- When you use LOG ERRORS, it is absolutely critical that you check the table immediately after the DML statement for errors from that statement. The SQL statement does not terminate with an exception, so looking at the table is THE ONLY WAY to know if anything went wrong! A common action at this point is to move the error information from your table-specific DML error log table to a persistent application error log table.
SELECT ora_err_mesg$, ora_err_rowid$, ora_err_tag$, last_name  
  FROM err$_employees  
 WHERE ROWNUM < 10 ;

-- Clean Up the Error Log Table
-- After checking the contents, I clean out the table, so the contents do not confuse me when I execute the next DML statement on the table.
BEGIN  
   DELETE FROM err$_employees;  

   COMMIT;  
END; 
/

-- Specify Limit on Rejections (Errors)
-- Suppose I am doing a bulk update, but I expect that very few errors will occur. If more than 10 row updates fail, something is wrong, and I want to simply stop. Then LOG ERRORS REJECT LIMIT 10 will do the trick.
BEGIN  
       UPDATE employees  
          SET first_name = first_name || first_name || first_name  
   LOG ERRORS REJECT LIMIT 10;  

   ROLLBACK;  
END; 
/

SELECT 'Number of errors = ' || COUNT ( * ) 
  FROM err$_employees ;