Number of rows returned by different JOINs

  • Comments posted to this topic are about the item Number of rows returned by different JOINs

  • Interesting one 🙂

  • Way too easy as you only have to check the first query to get to the right answer.

    Thanks for the effort though.

    Need an answer? No, you need a question
    My blog at https://sqlkover.com.
    MCSE Business Intelligence - Microsoft Data Platform MVP

  • Finally a question for my level.

    Thanks

  • Koen Verbeeck (7/3/2014)


    Way too easy as you only have to check the first query to get to the right answer.

    Thanks for the effort though.

    +1

    (did the same) Thank you for the post, nice one.

    ww; Raghu
    --
    The first and the hardest SQL statement I have wrote- "select * from customers" - and I was happy and felt smart.

  • Definitely way too easy.

    Still easy, but if table B would have the values 1 and 2, then at least you could have explained something about the different join types.

  • Mighty (7/3/2014)


    Definitely way too easy.

    Still easy, but if table B would have the values 1 and 2, then at least you could have explained something about the different join types.

    This should hold for some time... (except CROSS)

    ww; Raghu
    --
    The first and the hardest SQL statement I have wrote- "select * from customers" - and I was happy and felt smart.

  • Raghavendra Mudugal (7/3/2014)


    Koen Verbeeck (7/3/2014)


    Way too easy as you only have to check the first query to get to the right answer.

    Thanks for the effort though.

    +1

    (did the same) Thank you for the post, nice one.

    +1

    Valid, only when all values are same like in the example.

    Igor Micev,
    My blog: www.igormicev.com

  • This was removed by the editor as SPAM

  • Nice question, thanks for sharing

  • Stewart "Arturius" Campbell (7/3/2014)


    Found myself thinking this was way too easy, where's the catch?

    only to find there wasn't one

    Nice question, thanks Abbas

    +1

    This took me way too long to answer, because I kept looking over it trying to figure out what the trick was. Ultimately I couldn't find it and went with the simple answer.

  • thanks for puting it together

  • Easy one, thanks. I needed an easy one after getting the last four in a row wrong.


    [font="Tahoma"]Personal blog relating fishing to database administration:[/font]

    [font="Comic Sans MS"]https://davegugg.wordpress.com[/url]/[/font]

  • david.gugg (7/3/2014)


    Easy one, thanks. I needed an easy one after getting the last four in a row wrong.

    ...been there... 🙂 totally agree.

    ww; Raghu
    --
    The first and the hardest SQL statement I have wrote- "select * from customers" - and I was happy and felt smart.

  • Nice question, although somewhat simple. However, the explanation given:

    The values in col1 in both the tables is matched against each other resulting in 6 rows for all the SELECT statements.

    is slightly incorrect. This statement is true for all of the join types, except the cross join, in which col1 is not matched between the tables; you just get all possible combinations. If table A contained 1,2,3, and table B contained 4,5, the cross join would still produce 6 rows.

    I suggest that you submit another QotD similar to this, but with more values in each table, such as table A containing 1,1,1,2,null,null and table B containing 1,1,3,null,null. That would be more challenging, especially with multiple nulls values to consider ("when does null=null?").

Viewing 15 posts - 1 through 15 (of 25 total)

You must be logged in to reply to this topic. Login to reply