SELECT a.user_id user_id,a.hotel_id hotel_id,CAST(hotel_name AS VARCHAR) FROM user_hotel AS a RIGHT JOIN hotel AS b ON a.hotel_id=b.id WHERE a.user_id IN (8);报错

根据你提供的 SQL 查询语句，可能是因为在 MySQL 中并没有 `VARCHAR` 数据类型，而是使用 `VARCHAR(n)` 表示可变长度的字符类型，其中 `n` 表示最大长度。因此，你可以将查询结果中的 `hotel_name` 转换为 `VARCHAR(255)` 类型，如下所示：

SELECT a.user_id user_id, a.hotel_id hotel_id, CAST(hotel_name AS VARCHAR(255)) FROM user_hotel AS a RIGHT JOIN hotel AS b ON a.hotel_id=b.id WHERE a.user_id IN (8);

这样就可以将查询结果中的 `hotel_name` 字段转换为 `VARCHAR` 类型了。同时，你还需要检查表中是否存在 `hotel_name` 字段，以及该字段是否为字符类型。如果该字段本来就是字符类型，那么不需要进行类型转换。

相关问题

编写存储过程 SELECT a.order_id, a.done_date, a.cust_id, a.subscriber_ins_id, a.access_num, c.dev_id, c.dev_name, c.corp_org, c.company_name, c.department_code, c.department_name, c.remarks FROM JOUR1.Om_Subscriber_202301 a LEFT JOIN JOUR1.om_order_202301 b ON a.order_id = b.order_id LEFT JOIN params1.sec_developer c ON b.dev_id = c.dev_id UNION ALL SELECT a.order_id, a.done_date, a.cust_id, a.subscriber_ins_id, a.access_num, c.dev_id, c.dev_name, c.corp_org, c.company_name, c.department_code, c.department_name, c.remarks FROM JOUR1.Om_Subscriber_202302 a LEFT JOIN JOUR1.om_order_202302 b ON a.order_id = b.order_id LEFT JOIN params1.sec_developer c ON b.dev_id = c.dev_id UNION ALL SELECT a.order_id, a.done_date, a.cust_id, a.subscriber_ins_id, a.access_num, c.dev_id, c.dev_name, c.corp_org, c.company_name, c.department_code, c.department_name, c.remarks FROM JOUR1.Om_Subscriber_202303 a LEFT JOIN JOUR1.om_order_202303 b ON a.order_id = b.order_id LEFT JOIN params1.sec_developer c ON b.dev_id = c.dev_id UNION ALL SELECT a.order_id, a.done_date, a.cust_id, a.subscriber_ins_id, a.access_num, c.dev_id, c.dev_name, c.corp_org, c.company_name, c.department_code, c.department_name, c.remarks FROM JOUR1.Om_Subscriber_202304 a LEFT JOIN JOUR1.om_order_202304 b ON a.order_id = b.order_id LEFT JOIN params1.sec_developer c ON b.dev_id = c.dev_id

你可以编写一个存储过程来执行这个查询。下面是一个示例：

CREATE OR REPLACE PROCEDURE get_data AS
BEGIN
  -- 创建临时表来保存结果
  CREATE GLOBAL TEMPORARY TABLE temp_data (
    order_id          NUMBER,
    done_date         DATE,
    cust_id           NUMBER,
    subscriber_ins_id NUMBER,
    access_num        VARCHAR2(100),
    dev_id            NUMBER,
    dev_name          VARCHAR2(100),
    corp_org          VARCHAR2(100),
    company_name      VARCHAR2(100),
    department_code   VARCHAR2(100),
    department_name   VARCHAR2(100),
    remarks           VARCHAR2(100)
  ) ON COMMIT PRESERVE ROWS;

  -- 第一个查询
  INSERT INTO temp_data
  SELECT a.order_id,
         a.done_date,
         a.cust_id,
         a.subscriber_ins_id,
         a.access_num,
         c.dev_id,
         c.dev_name,
         c.corp_org,
         c.company_name,
         c.department_code,
         c.department_name,
         c.remarks
  FROM JOUR1.Om_Subscriber_202301 a
  LEFT JOIN JOUR1.om_order_202301 b
    ON a.order_id = b.order_id
  LEFT JOIN params1.sec_developer c
    ON b.dev_id = c.dev_id;

  -- 后续查询使用UNION ALL连接
  INSERT INTO temp_data
  SELECT a.order_id,
         a.done_date,
         a.cust_id,
         a.subscriber_ins_id,
         a.access_num,
         c.dev_id,
         c.dev_name,
         c.corp_org,
         c.company_name,
         c.department_code,
         c.department_name,
         c.remarks
  FROM JOUR1.Om_Subscriber_202302 a
  LEFT JOIN JOUR1.om_order_202302 b
    ON a.order_id = b.order_id
  LEFT JOIN params1.sec_developer c
    ON b.dev_id = c.dev_id;

  INSERT INTO temp_data
  SELECT a.order_id,
         a.done_date,
         a.cust_id,
         a.subscriber_ins_id,
         a.access_num,
         c.dev_id,
         c.dev_name,
         c.corp_org,
         c.company_name,
         c.department_code,
         c.department_name,
         c.remarks
  FROM JOUR1.Om_Subscriber_202303 a
  LEFT JOIN JOUR1.om_order_202303 b
    ON a.order_id = b.order_id
  LEFT JOIN params1.sec_developer c
    ON b.dev_id = c.dev_id;

  INSERT INTO temp_data
  SELECT a.order_id,
         a.done_date,
         a.cust_id,
         a.subscriber_ins_id,
         a.access_num,
         c.dev_id,
         c.dev_name,
         c.corp_org,
         c.company_name,
         c.department_code,
         c.department_name,
         c.remarks
  FROM JOUR1.Om_Subscriber_202304 a
  LEFT JOIN JOUR1.om_order_202304 b
    ON a.order_id = b.order_id
  LEFT JOIN params1.sec_developer c
    ON b.dev_id = c.dev_id;

  -- 查询结果
  SELECT * FROM temp_data;

  -- 删除临时表
  DROP TABLE temp_data;
END;
/

这个存储过程创建了一个临时表 `temp_data` 来保存查询结果，并将每个查询的结果插入到临时表中。最后，通过查询 `temp_data` 表来获取结果。

请注意，根据你的实际需求和数据库结构，你可能需要修改表和列的定义，以及查询的逻辑。确保在执行存储过程之前，已经创建了所需的表和索引。

达梦数据库 utl_raw.cast_to_varchar2 函数

在达梦（DM）数据库中，`UTL_RAW.CAST_TO_VARCHAR2`函数用于将RAW（原始二进制数据类型）转换为VARCHAR2字符数据类型。这个函数通常用于处理存储在RAW列中的二进制数据并将其转化为可读的文本形式。

以下是如何使用`UTL_RAW.CAST_TO_VARCHAR2`的一个示例：

-- 假设我们有一个RAW类型的变量containing_data
DECLARE
   containing_data RAW(20);
BEGIN
   -- 假设containing_data已填充了一些二进制数据
   containing_data := UTL_RAW.HEXTORAW('E997AEE997AE6D61636C65616E'); -- 使用cast_to_varchar2函数转换为VARCHAR2
   SELECT UTL_RAW.CAST_TO_VARCHAR2(containing_data) AS converted_text
   FROM DUAL;
   
   -- 结果会显示为 'maclean'
   -- SQL> SELECT UTL_RAW.CAST_TO_VARCHAR2('E997AEE997AE6D61636C65616E') as maclean FROM dual;
   -- converted_text
   -- -------------
   -- maclean
END;
/

在这个例子中，原始的二进制数据'E997AEE997AE6D61636C65616E'被转换成了字符字符串'maclean'。