oracle sql identify duplicates code example

Example 1: oracle finding duplicate records

SELECT column_name, COUNT(column_name)
FROM table_name
GROUP BY column_name
HAVING COUNT(column_name) > 1;

Example 2: oracle duplicate table

-- Copy a table (datas, columns and storage parameters)
CREATE TABLE my_new_table AS SELECT * FROM my_source_table;
-- Use NOLOGGING, and PARALLEL if allowed for faster copy
CREATE TABLE my_new_table
    PARALLEL 10 NOLOGGING
AS
SELECT /*+ parallel(10) */ * FROM my_source_table;
-- To create an empty table:
CREATE TABLE my_new_table AS SELECT * FROM my_source_table
	WHERE rownum = 0;