code: public int count(Connection conn, Entity where) throws SQLException {
  		checkConn(conn);
  		
  		final Query query = new Query(SqlUtil.buildConditions(where), where.getTableName());
  		PreparedStatement ps = null;
  		try {
  			ps = dialect.psForCount(conn, query);
  			return SqlExecutor.query(ps, new NumberHandler()).intValue();
  		} catch (SQLException e) {
  			throw e;
  		} finally {
  			DbUtil.close(ps);
  		}
  	}
docs: 结果的条目数
  @param conn 数据库连接对象
  @param where 查询条件
  @return 复合条件的结果数
  @throws SQLException SQL执行异常