How to write SQL statement with dynamic where clause?

How to Write a SQL statement to display the repeated rows of the table below:?

• Write a SQL statement to display the repeated rows of the table below: Field Type Null Key Default Extra doc_id varchar(1000) NO PARTIAL NO topic_id varchar(45) NO PARTIAL NO doc_headline text NO NO NO doc_text text NO NO NO

• Answer:

  Ok, I will assume that 'topic_id' is the criteria for determining if the row is repeated (i.e. topic_id is the same on two or more items). I am giving you a generic way of dealing with the problem. You can adjust the query by changing the column name if the semantics of "repeated" are different: SELECT topic_id, count(topic_id) FROM documents GROUP BY topic_id HAVING count(topic_id) > 1