MS Access外部将多个字段连接到单个记录

Question

我需要执行与此处所示完全相同的操作:INNER或LEFT将多个表记录连接到单个行但是它在MS Access查询中工作.

以下是场景:

---

电话表

+----------------+-------------+
| Field          | Type        |
+----------------+-------------+
| f_id           | int(15)     |
| f_client_id    | int(11)     |
| f_phone_type   | varchar(50) |
| f_phone_number | varchar(13) |
+----------------+-------------+

客户表

+-----------------------------+--------------+------+-----+
| Field                       | Type         | Null | Key |
+-----------------------------+--------------+------+-----+
| f_id                        | int(15)      | NO   | PRI |
| f_first_name                | varchar(13)  | YES  | MUL |
| f_mi                        | char(1)      | YES  |     |
| f_last_name                 | varchar(20)  | NO   | MUL |
+-----------------------------+--------------+------+-----+

使用标准的LEFT或INNER连接,我得到这样的结果:

+------------+------------+--------------+
| name       | Phone Type | Phone Number |
+------------+------------+--------------+
| John Smith | Home       | 712-555-6987 |
| John Smith | Work       | 712-555-1236 |
+------------+------------+--------------+

我需要一个查询,它将为我提供属于给定客户端的工作和家庭号码:

+------------+----------------+--------------+
| Name       | Work Number    | Home Number  |
+------------+----------------+--------------+
| John Smith | 712-555-1236   | 712-555-6987 |
+------------+----------------+--------------+

---

SQL中的解决方案是

SELECT CONCAT(c.f_first_name, ' ', c.f_last_name) as Client_Name, 
       wp.f_phone_number as Work_Number,
       hp.f_phone_number as Home_Number

  FROM clients c
       LEFT OUTER JOIN phone hp
       ON hp.f_client_id = c.f_id
    AND
       hp.phone_type = 'home'
       LEFT OUTER JOIN phone wp
       ON wp.f_client_id = c.f_id
    AND
       wp.phone_type = 'work'

但是,这不会转换为MS Access,加入失败.通过Access完成同样的事情的最佳方法是什么？

Answer 1

你还没有发现两个问题.

1. Access或其数据库引擎中没有CONCAT()函数
2. 您的查询尝试使用phone_type,但实际字段名称为f_phone_type

当连接两个以上的表时,Access'数据库引擎需要括号.通过使用查询设计器来设置连接,这是最简单的方法.查询设计者也会将LEFT JOIN替换为LEFT OUTER JOIN; 这两种方式都适用于Access 2003.

这个很容易在查询设计器中构建,但只返回具有home和work数字的客户端的行.我用它作为起点,后来调整了类似你原来的ON子句.

SELECT
    c.f_first_name & " " & c.f_last_name AS [Name],
    wp.f_phone_number AS [Work Number],
    hp.f_phone_number AS [Home Number]
FROM
    (Clients AS c
    LEFT JOIN Phones AS hp
    ON c.f_id = hp.f_client_id)
    LEFT JOIN Phones AS wp
    ON c.f_id = wp.f_client_id
WHERE
    hp.f_phone_type='Home'
    AND wp.f_phone_type='Work';

将这些WHERE条件移动到ON表达式(如SQL Server示例中)将返回所有客户端,无论您是否有任何电话号码存档.但是,该方法将需要围绕ON表达式的括号.并且这些JOINS无法在查询设计器中显示.

SELECT
    c.f_first_name & " " & c.f_last_name AS [Name],
    wp.f_phone_number AS [Work Number],
    hp.f_phone_number AS [Home Number]
FROM
    (Clients AS c
    LEFT JOIN Phones AS hp
    ON (c.f_id = hp.f_client_id AND hp.f_phone_type='Home'))
    LEFT JOIN Phones AS wp
    ON (c.f_id = wp.f_client_id AND wp.f_phone_type='Work');

更新:对于我自己,我宁愿用子查询来做这件事.

SELECT
    c.f_first_name & " " & c.f_last_name AS [Name],
    wp.f_phone_number AS [Work Number],
    hp.f_phone_number AS [Home Number]
FROM
    (Clients AS c
    LEFT JOIN [
        SELECT f_client_id, f_phone_number
        FROM Phones
        WHERE f_phone_type='Home'
    ]. AS hp
    ON c.f_id = hp.f_client_id)
    LEFT JOIN [
        SELECT f_client_id, f_phone_number
        FROM Phones
        WHERE f_phone_type='Work'
    ]. AS wp
    ON c.f_id = wp.f_client_id;