CODEWITHSUNDEEP
mysqlsqlforeign-keysprimary-key
jobun
jobun

Reputation: 157

Get A Threaded Message by Recipients

I have database schemas like this:

users
USERNAME (PK), SEX
Alex, F
John, M
Troy, M
Matt, M

messages
ID (PK), CREATOR (FK users), DATE_CREATED
1, John, 2012-04-15
2, Troy, 2012-04-16

message_recipients
ID, MESSAGE_ID (FK messages), RECIPIENT (FK users), DATE
1, 1, John, 2012-04-15
2, 1, Troy, 2012-04-15
3, 1, Matt, 2012-04-15
4, 2, Alex, 2012-04-16
4, 2, John, 2012-04-16

The challenge is this, I want to get a message ID that has John, Troy and Matt as the recipients only.

This is my query:

SELECT mr1.MESSAGE_ID
FROM message_recipients mr1, message_recipients mr2
WHERE mr1.MESSAGE_ID = mr2.MESSAGE_ID
  AND mr1.RECIPIENT = mr2.RECIPIENT
  AND mr2.RECIPIENT = 'John'
  AND mr2.RECIPIENT = 'Troy'
  AND mr2.RECIPIENT = 'Matt'

The SQL above shows No Results.

If I do this query:

SELECT mr1.MESSAGE_ID
FROM message_recipients mr1, message_recipients mr2
WHERE mr1.MESSAGE_ID = mr2.MESSAGE_ID
  AND mr1.RECIPIENT_ID = mr2.RECIPIENT_ID
  AND (mr2.RECIPIENT_ID = 'John'
  OR mr2.RECIPIENT_ID = 'Troy'
  OR mr2.RECIPIENT_ID = 'Matt')
GROUP BY mr1.MESSAGE_ID

The results:

MESSAGE_ID
1
2

The above results are incorrect because what I want to see is only 1 (MESSAGE_ID) as the result.

What did I do wrong? Could someone enlighten me?

Thank you very much, John

Upvotes: 1

Views: 75

Answers (3)

Ankit Sharma
Ankit Sharma

Reputation: 4069

Give it a try-

SELECT mr1.MESSAGE_ID
FROM message_recipients mr1, message_recipients mr2
WHERE mr1.MESSAGE_ID = mr2.MESSAGE_ID
  AND mr1.RECIPIENT = mr2.RECIPIENT
  AND mr2.RECIPIENT = 'John'
  AND mr2.RECIPIENT in ('Troy','Matt')

Upvotes: 0

Arion
Arion

Reputation: 31249

I am not really sure what you want. But a column can't be 3 things. You can just the IN syntax . Like this:

SELECT mr1.MESSAGE_ID
FROM message_recipients mr1, message_recipients mr2
WHERE mr1.MESSAGE_ID = mr2.MESSAGE_ID
  AND mr1.RECIPIENT = mr2.RECIPIENT
  AND mr2.RECIPIENT IN('John','Troy','Matt')

Or the OR syntax like this:

SELECT mr1.MESSAGE_ID
    FROM message_recipients mr1, message_recipients mr2
    WHERE mr1.MESSAGE_ID = mr2.MESSAGE_ID
      AND mr1.RECIPIENT = mr2.RECIPIENT
      AND 
      (
      mr2.RECIPIENT = 'John'
      OR mr2.RECIPIENT = 'Troy'
      OR mr2.RECIPIENT = 'Matt'
      )

EDIT

I am still not sure what you want. But it kinda sound like you want something like this:

SELECT
    m.ID AS MESSAGE_ID,
    m.CREATOR,
    mr.RECIPIENT,
    mr2.RECIPIENT
FROM
    messages AS m
    LEFT JOIN message_recipients AS mr
        ON m.ID=mr.MESSAGE_ID
        AND mr.RECIPIENT='Troy'
    LEFT JOIN message_recipients AS mr2
        ON m.ID=mr2.MESSAGE_ID
        AND mr2.RECIPIENT='Matt'
WHERE
    m.CREATOR='John'

Upvotes: 1

user319198
user319198

Reputation:

I think you should Use OR instead of AND

Try below :

SELECT mr1.MESSAGE_ID
FROM message_recipients mr1 LEFT JOIN message_recipients mr2 
ON mr1.MESSAGE_ID = mr2.MESSAGE_ID
WHERE  mr1.RECIPIENT = mr2.RECIPIENT
  AND ( mr2.RECIPIENT = 'John'
  OR mr2.RECIPIENT = 'Troy'
  OR mr2.RECIPIENT = 'Matt')

Upvotes: 0

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