MySQL：从多个表中选择字段来显示记录来自哪个表

Question

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

另外，email_id很可能存在于多个表中（即，一封电子邮件可能是所有者和经理，或者甚至全部3个）。

这里是我迄今：

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 

该查询实际上完美的作品。它会逐个删除表中的重复项，但将其保留在多个表中。我仍然无法知道每个表来自哪个表。我试图修改这个查询：

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，因为不是所有的表都有相同的列。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），则查询起作用，但所有表似乎具有相同的字段。不知道为什么。

最终，我想在返回的记录集中没有重复的电子邮件地址，并且每个记录都有类似email = 'email address', owner = 'yes/no', manager = 'yes/no', employee = 'yes/no'。

有关如何完成此任何想法？如果您需要更多信息，请点评。谢谢！

Answer 1

添加“表格名”列每组结果来确定哪些表中的结果从

0123来了

(
    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 
) 

或者为每个结果块添加3列。即添加* is_owner，IS_MANAGER，is_employee *到所有 3选择块

Answer 2

您可以通过每一行以这种方式迫使值做到这一点：

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

如果你想从整个结果集删除重复项（其中“删除重复”我知道你想从电子邮件表的任何），你应该换行，在外部查询和应用组：

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 

Answer 3

 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;