Document count increase every time with jdbc driver

input {
  jdbc {
    jdbc_driver_library => ""
    jdbc_driver_class => "com.microsoft.sqlserver.jdbc.SQLServerDriver"
    jdbc_connection_string => "jdbc:sqlserver://aasdf;instanceName=aaSQL;databasename=aaa"
    jdbc_user => "elkuser"
    jdbc_password => "elk1234"
    schedule => "* * * * *"
    statement => "SELECT * FROM Orders;"
  }
}

The document count always increase even if there is no movement in my SQL Table Orders.
How come it is possible ?.

The count in the Orders table should match the document count of elastic search right ?.

Thanks a lot for your help