code: public static boolean delete(String tableName, String primaryKey, Record record) {
  		return MAIN.delete(tableName, primaryKey, record);
  	}
docs: Delete record.
  <pre>
  Example:
  boolean succeed = Db.delete("user", "id", user);
  </pre>
  @param tableName the table name of the table
  @param primaryKey the primary key of the table, composite primary key is separated by comma character: ","
  @param record the record
  @return true if delete succeed otherwise false