Question

I’m developing a information system, and I’ve and message center. And I want to display the messages like Outlook or Gmail “conversation”.

In my message table I have the following columns:

• MessageId (PK)
• Date
• From (FK)
• To (FK)
• Body
• Subject
• State
• Subject
• ReplyId (FK), null

First I get the messages that don’t have replyId, to show the “latest” message.

But I don’t get the conversation, when any one click on message… 🙁

Any one could help me with the query?

Thanks in advance

EDIT:
I add an extra field to the table, the Id of last reply to the conversation, so I can get all conversation message at one time!

🙂

Answer 1

You want to use a CTE to accomplish this, which is essentially a parent-child query:

declare @MessageId int = 3;

with Conversations as
(
    select
        MessageId,
        [Date],
        [From],
        [To],
        Body,
        [Subject],
        [State],
        ReplyId,
        CAST(MessageId as varchar(max)) + '-' as hierarchy,
        CAST(MessageId as varchar(max)) + '-' as TopMessageId
    from
        Messages
    where
        replyid is null
    union all
    select
        m.MessageId,
        m.[Date],
        m.[From],
        m.[To],
        m.Body,
        m.[Subject],
        m.[State],
        m.ReplyId,
        c.hierarchy + CAST(m.MessageId as varchar(max)) + '-' as hierarchy,
        c.TopMessageId
    from
        Conversations c
        inner join Messages m on
            c.MessageId = m.ReplyId
)

select
    c2.MessageId,
    c2.[Date],
    c2.[From],
    c2.[To],
    c2.Body,
    c2.[Subject],
    c2.[State],
    c2.ReplyId
from
    Conversations c1
    inner join Conversations c2 on
        c2.hierarchy like c1.TopMessageId + '%'
where
    c1.MessageId = @MessageId
order by c2.[Date] desc

If you’re using SQL Server 2008, you may want to look into using a hierarchyid column on your table to avoid the CTE all together.