将 4 个表中的数据合并到一列/字段中答案

【问题标题】：Combining data from 4 tables into one column/field将 4 个表中的数据合并到一列/字段中
【发布时间】：2013-01-25 12:39:01
【问题描述】：

我需要在 MS Access 2010 中创建一个查询，将来自 4 个不同表的数据组合在一列中。

表格定义如下；

Table 1: date, country, channel, calls_in
Table 2: date, country, channel, calls_out
Table 3: date, country, channel, email
Table 4: date, country, channel, chat

查询应如下所示：

Query 1: Date, country, channel, contacts

联系人列应结合相应日期、国家和渠道的 4 种联系人类型（即calls_in/out、电子邮件和聊天）。

所有 4 个表格的日期和国家/地区都相同。频道特定于每个表。

我一直在努力完成这项工作，但无法理解它。

【问题讨论】：

标签： sql ms-access ms-access-2010

【解决方案1】：

你可能会追求这个：

SELECT
  all_contacts.date,
  all_contacts.country,
  all_contacts.channel,
  "calls in: " & [calls_in] & ", calls out: " & [calls_out] & ", email: " & [email] & ", chat " & [chat] AS contacts
FROM
  ((((select date, country, channel from [Table 1] union
      select date, country, channel from [Table 2] union
      select date, country, channel from [Table 3] union
      select date, country, channel from [Table 4])  AS all_contacts
  LEFT JOIN [Table 1] ON (all_contacts.channel = [Table 1].channel) AND (all_contacts.country = [Table 1].country) AND (all_contacts.date = [Table 1].date))
  LEFT JOIN [Table 2] ON (all_contacts.channel = [Table 2].channel) AND (all_contacts.country = [Table 2].country) AND (all_contacts.date = [Table 2].date))
  LEFT JOIN [Table 3] ON (all_contacts.channel = [Table 3].channel) AND (all_contacts.country = [Table 3].country) AND (all_contacts.date = [Table 3].date))
  LEFT JOIN [Table 4] ON (all_contacts.channel = [Table 4].channel) AND (all_contacts.country = [Table 4].country) AND (all_contacts.date = [Table 4].date);

由于 MS-Access 不支持 FULL OUTER JOINS，并且没有像 GROUP_CONCAT 这样的聚合函数，我将加入一个 UNION 子查询，其中包含每个表的所有日期、国家和频道，我然后将所有联系人（calls_in、calls_out、电子邮件和聊天）合并到一个单元格中。

【讨论】：

【解决方案2】：

使用UNION（隐式不同）或UNION ALL：

SELECT date, country, channel, 'calls_in' AS ContactType, calls_in AS ContactData
FROM table1
UNION ALL
SELECT date, country, channel, 'calls_out', calls_out        
FROM table2
UNION ALL
SELECT date, country, channel, 'email', email
FROM table3
UNION ALL
SELECT date, country, channel, 'chat', chat
FROM table4;

这将为您提供四个表中的所有数据，以及calls_in、calls_out、email 和chat 三种类型的新列chat 以及它们的数据。

【讨论】：

您可以使用联系人类型字段并重命名联系人类型列来改进它，这样它就不会以 calls_in
我在想SELECT date, country, channel, "Call-in" As Contacts, calls_in AS ContactData
@Remou 更新，再次感谢。这应该是你的答案。顺便说一句，"call-in" 在访问中是一个有效的文字值吗？它不应该是标识符而不是文字值吗？我写'calls_in'这样可以吗？
是的，它是 -- SELECT "abc" as atext, 1 as anumber, Date() as adate ...`。您可能会使用单引号，双引号更常见。

【解决方案3】：

我想稍微改进一下 Mahmoud 的回答：

SELECT date, country, channel, calls_in, 'Calls_in' as ContactType  FROM table1
UNION ALL
SELECT date, country, channel, calls_out, 'Calls_out' as ContactType FROM table2
UNION ALL
SELECT date, country, channel, email, 'email' as ContactType FROM table3
UNION ALL
SELECT date, country, channel, chat, 'Calls_in' as ContactType FROM table4;

但我必须说，很明显数据库可以进行一些规范化。如果您可以修改数据库，则可以很容易地将所有数据放在一个表中，并且只需有一个字段来跟踪您使用的通信类型。

【讨论】：