-1

我有 3 个表格，其中包含非常相似的信息。这些表是所有者、经理和员工。我试图从所有 3 个表中提取信息，同时仍然了解每条记录来自哪个表。我也不想重复。所有表都有一个 email_id，它与email我要加入的表相关。

此外，email_id 很可能会存在于多个表中（即，电子邮件可能是所有者和管理员，甚至可能是所有 3 个）。

到目前为止，这是我所拥有的：

SELECT email
FROM (
    (
        SELECT e.email
        FROM `owners` as o
        LEFT JOIN `email` as e
        ON e.email_id = o.email_id
        WHERE o.company_id = 3
        GROUP BY e.email
    )
    UNION ALL
    (
        SELECT e.email
        FROM `managers` as m
        LEFT JOIN `email` as e
        ON e.email_id = m.email_id
        WHERE m.company_id = 3
        GROUP BY e.email
    )
    UNION ALL
    (
        SELECT e.email
        FROM `employees` as emp
        LEFT JOIN `email` as e
        ON e.email_id = emp.email_id
        WHERE v.company_id = 3
        GROUP BY e.email
    )
) as `people`
ORDER BY email ASC

这个查询实际上工作得很好。它单独从表中删除重复项，但将它们保留在多个表中。我仍然无法知道每个表来自哪个表。我试图将查询修改为：

SELECT email, owner, manager, employee
FROM (
    (
        SELECT e.email, 'yes' as owner
        FROM `owners` as o
        LEFT JOIN `email` as e
        ON e.email_id = o.email_id
        WHERE o.company_id = 3
        GROUP BY e.email
    )
    UNION ALL
    (
        SELECT e.email, 'yes' as manager
        FROM `managers` as m
        LEFT JOIN `email` as e
        ON e.email_id = m.email_id
        WHERE m.company_id = 3
        GROUP BY e.email
    )
    UNION ALL
    (
        SELECT e.email, 'yes' as employee
        FROM `employees` as emp
        LEFT JOIN `email` as e
        ON e.email_id = emp.email_id
        WHERE v.company_id = 3
        GROUP BY e.email
    )
) as `people`
ORDER BY email ASC

这不起作用，因为并非所有表都具有相同的列。如果我将所有字段添加到所有表（即SELECT e.email, 'yes' as owner, '' as manager, '' as employee），则查询有效，但所有表似乎都具有相同的字段。不知道为什么。

最终，我希望返回的记录集中没有重复的电子邮件地址，并且每条记录都类似于email = 'email address', owner = 'yes/no', manager = 'yes/no', employee = 'yes/no'.

关于如何做到这一点的任何想法？如果您需要更多信息，请发表评论。谢谢！

4

3 回答 3

1

Add a "table_name" column to each set of results to identify which table the results came from

(
    SELECT e.email, 'owners' as table_name
    FROM `owners` as o
    LEFT JOIN `email` as e
    ON e.email_id = o.email_id
    WHERE o.company_id = 3
    GROUP BY e.email
)
UNION ALL
(
    SELECT e.email, 'managers' as table_name
    FROM `managers` as m
    LEFT JOIN `email` as e
    ON e.email_id = m.email_id
    WHERE m.company_id = 3
    GROUP BY e.email
)
UNION ALL
(
    SELECT e.email, 'employees' as table_name
    FROM `employees` as emp
    LEFT JOIN `email` as e
    ON e.email_id = emp.email_id
    WHERE v.company_id = 3
    GROUP BY e.email
)

Alternatively add 3 columns to each block of results. i.e. add *is_owner, is_manager, is_employee* to all 3 select blocks

于 2013-10-24T16:09:42.127 回答
0

您可以通过这种方式在每一行中强制一个值来做到这一点：

select t1.field1, t1.field2, 'YourFirstTable' as fromTable from t1
union all
select t2.field1, t2.field2, 'YourSecondTable' from t2

如果您想从整个结果集中删除重复项（通过“删除重复项”，我知道您想要来自任何表的电子邮件），您应该将其包装在外部查询中并通过以下方式应用组：

select field1, field2, max(fromTable)
    select t1.field1 as field1, t1.field2 as field2, 'YourFirstTable' as fromTable from t1
    union all
    select t2.field1, t2.field2, 'YourSecondTable' from t2
group by field1, field2
于 2013-10-24T16:06:19.900 回答
0 
        SELECT e.email,"owners" AS people
        FROM `owners` as o
        LEFT JOIN `email` as e
        ON e.email_id = o.email_id
        WHERE o.company_id = 3
        GROUP BY e.email
     UNION ALL
        SELECT e.email,"managers" AS people
        FROM `managers` as m
        LEFT JOIN `email` as e
        ON e.email_id = m.email_id
        WHERE m.company_id = 3
        GROUP BY e.email
    UNION ALL
        SELECT e.email,"employees" AS people
        FROM `employees` as emp
        LEFT JOIN `email` as e
        ON e.email_id = emp.email_id
        WHERE v.company_id = 3
        GROUP BY e.email;
于 2013-10-24T16:12:01.190 回答