insert unique in database sqflite code example

Example 1: sqlite insert if not exists

#id column is assumed to be primary key

INSERT INTO destination_table(id,name) 
SELECT id, name
FROM source_table s
WHERE NOT EXISTS (
  SELECT 1
  FROM destination_table d
  WHERE d.id = s.id
);

Example 2: sqlite unique

sqlite uniue
-------------------------        
CREATE TABLE contacts(
  contact_id INTEGER PRIMARY KEY,
  first_name TEXT,
  last_name TEXT,
  email TEXT NOT NULL UNIQUE
);