title: Checking duplicated when filling SQL Table using SQLAlchemy/Pandas to_SQL
body: <p>I would like to dump data into my mysql database. If I want to add addtional data, I am using the same cvs file as shown below but extended with the additional line. </p>
  
  <p>If i restart my code the data just gets included again plus the additional line. This means my data doubles plus one. </p>
  
  <p>How can I check the data base and exclude doubles, so just that the newest line gets included? </p>
  
  <p>The initial csv file looks the following:</p>
  
  <pre><code>Ticker;Name;Country
  A;Pablo;USA
  B;Nico;USA
  C;Dimi;USA
  D;George;USA
  E;Will;USA
  F;Paul;USA
  </code></pre>
  
  <p>Extended csv File:</p>
  
  <pre><code>Ticker;Name;Country
  A;Pablo;USA
  B;Nico;USA
  C;Dimi;USA
  D;George;USA
  E;Will;USA
  F;Paul;USA
  G;Tom;Russia
  </code></pre>
  
  <p>The code looks like the following:</p>
  
  <pre><code>import sqlalchemy as sqlal
  import pandas as pd
  
  mysql_engine = sqlal.create_engine('mysql+mysqlconnector://xxx/Test_Schema',poolclass=sqlal.pool.NullPool)
  
  mysql_engine.raw_connection()
  
  if not mysql_engine.dialect.has_table(mysql_engine, 'master_data'):  
      metadata = sqlal.MetaData(mysql_engine)
  
      sqlal.Table('master_data', metadata,
                  sqlal.Column('Ticker', sqlal.String(20), nullable=False, primary_key=True),
                  sqlal.Column('Name', sqlal.String(250), nullable=True),
                  sqlal.Column('Country', sqlal.String(10), nullable=True)
      )
      metadata.create_all(mysql_engine)  
  
  df_csv = pd.read_csv('TestFile.csv', encoding='cp1252', sep=';', index_col=0).dropna()
  print(df_csv)
  df_csv.to_sql(name='master_data', con=mysql_engine, if_exists = 'append', chunksize=900, index=True)
  </code></pre>