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Thread: Massive query, where NOT IN does not appear to work?

  1. #1
    Join Date
    Nov 2012

    Massive query, where NOT IN does not appear to work?


    I'll keep it to the point so we can get down to the nitty gritty!

    Table: tags
    Fields: tid INT, tname VARCHAR

    Table: uploads
    Fields: uid INT, ufile VARCHAR

    Table: tags_upoads
    Fields: tuid INT, tid INT, uid INT

    Step 1: From a webpage, a user uploads an image. The filepath to the upload is stored in the uploads table.

    Step 2: A user can then assign tags to an upload to describe its data. When a tag is submitted to the server, it checks against the database to see if it already exists, and if it doesn't it will create a new one.

    Step 3: Then the server will link those tag ID's to the upload ID using the tags_uploads table. So, uploads can have many tags.

    For reporting purposes, I would like to generate a result from the SQL server that meets the following conditions:

    * Shows distinct uploaded filenames
    * Only if the tag ID matches a certain tag number(s)
    * Only if the tag ID does not match other certain tag number(s)
    * Ordered by the popularity of the tags selected (number of times the tag ID has been assigned to an upload ID)

    However, imagine now that some uploads are tagged with a tag ID of 5 AND 6, but I want to show the uploads that are tagged 5 and exclude the uploads that are tagged with 6. How is that done?

    Imagine this data set in tags_uploads for this example:
    tuid=1, uid=1, tid=5
    tuid=2, uid=1, tid=6
    tuid=3, uid=2, tid=5
    tuid=4, uid=2, tid=6
    tuid=5, uid=3, tid=5

    In this example, uid's 1 and 2 are tagged with tid's 5 and 6. Only uid 5 is tagged with just 5 on its own.

    However these results need to be pulled back as part of an extremely large query which selects just distinct uploads, which is as follows:

    SELECT uploads.uid, uploads.ufile, tu.tid, counter.tidcount
    FROM uploads
    SELECT DISTINCT tags_uploads.uid, tags_uploads.tid
    FROM tags_uploads
    WHERE tags_uploads.tid
    IN ( 5 ) 
    AND tags_uploads.tid NOT 
    IN ( 6 ) 
    GROUP BY tags_uploads.uid
    ) AS tu ON uploads.uid = tu.uid
    INNER JOIN tags ON tags.tid = tu.tid
    SELECT tags_uploads.tid, COUNT( * ) AS tidcount
    FROM tags_uploads
    WHERE tags_uploads.tid
    IN ( 5 ) 
    AND tags_uploads.tid NOT 
    IN ( 6 ) 
    GROUP BY tags_uploads.tid
    ) AS counter ON tu.tid = counter.tid
    ORDER BY counter.tidcount DESC , uploads.uid DESC
    If I remove the code that says AND tags_uploads.tid NOT IN (6) from both subqueries, then I receive the exact same set of results.

    Please can somebody explain what I am missing here, and what is required for this to now work?

    I feel that this is an exceptionally complex question and I really will put my thanks out to the person that can help me with this. I'd even consider payment in some form.

    Thanks and good luck

  2. #2
    Join Date
    Nov 2012
    Perhaps a better way to visualise the data would be like this:

    uid = 1, ufile = redapple1.jpg
    uid = 2, ufile = redapple2.jpg
    uid = 3, ufile = greenapple.jpg

    tid = 1, tname = apple
    tid = 2, tname = red
    tid = 3, tname = green

    tuid = 1, tid = 1, uid = 1
    tuid = 2, tid = 1, uid = 2
    tuid = 3, tid = 1, uid = 3
    tuid = 4, tid = 2, uid = 1
    tuid = 5, tid = 2, uid = 2
    tuid = 6, tid = 3, uid = 3

    So we have 3 pictures of apples. All 3 are tagged as apple. 2 are tagged as red and one is tagged as green.

    If I wanted to show pictures of apples, but not red apples, I think the query should be this:

    SELECT uid FROM tags_uploads WHERE tid IN (1) AND tid NOT IN (2)
    Which should bring back just one result of the green apple, right? Well, it brings back all results. So I believe I am missing some crucial stage of logic here!

    Again, thanks in advance for helping out a poor soul.

  3. #3
    Join Date
    Nov 2012
    Also in the above, if you just run a query to show NOT apple's, you still get green's and red's, which are apples

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