code: public String getSimpleCountSql(final String sql, String name) {
          StringBuilder stringBuilder = new StringBuilder(sql.length() + 40);
          stringBuilder.append("select count(");
          stringBuilder.append(name);
          stringBuilder.append(") from (");
          stringBuilder.append(sql);
          stringBuilder.append(") tmp_count");
          return stringBuilder.toString();
      }
docs: 获取普通的Count-sql
  
  @param sql 原查询sql
  @return 返回count查询sql