How can I do an insert where not exists?

Question

I\'d like to combine an insert query with a \"where not exists\" so as not to violate PK constraints. However, syntax such as the following gives me an Incorrect synta

Answer 1

None of the examples worked for me... so I suggest this example:

INSERT INTO database_name.table_name(column_name)
SELECT column_name
  FROM database_name.table_name
 WHERE NOT EXISTS (SELECT NULL
                     FROM database_name.table_name
                    WHERE column_name = 'Column Value')