Re^4: (OT) MySQL query to limit and sort

Hi.

Sorry to bug you, you've been much help already. I am confused by this particular code.

   select baz.id, foo.name
    from foo,                    -- regular table
    ( 
       select id, frob from bar
    ) baz                        -- a sub-select

    where foo.id = baz.frob      -- something that joins the two
[download]

I know it's pseudo code but I was wondering if perhaps you could show me a small working sample with columns: id, url, images and Total? I am pretty confused by what you mean here. The table is "temp".

Thank you.

Comment on Re^4: (OT) MySQL query to limit and sort Download Code

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Re^5: (OT) MySQL query to limit and sort by rhesa (Vicar) on Feb 06, 2006 at 01:31 UTC
Here's your original request based on the column and table names you gave us: `select id, url, images, Total from ( select * from temp order by id desc limit 10 ) last10 order by Total desc;` [download] As for my pseudo-code you're confused about, that's only relevant if you have two tables that you might want to cross reference. As a more realistic example, suppose you have a database with Customers and Orders, and you want to find out your top ten buyers. You could do that like this: select Customers.name, sales.amount -- select na +me and total amount spent. from Customers, ( -- a sub-sel +ect to find the 10 best buyers. select customer_id, sum(order_amount) as amount -- This sele +cts a column and an aggregate from Orders -- from the +real table Orders. group by customer_id order by amount desc limit 10 ) sales -- we name t +his sub-select "sales". where sales.customer_id = Customers.id -- we INNER +JOIN the two "tables", -- so we can + cross-reference Orders against Customers. [download] As you can see, the "sales" sub-select isn't a real table in the database, but within this query we can treat it as if it were. We can select columns from it, and put extra constraints on it in a `where` clause. I hope it's a bit clearer now :)	[reply] [d/l] [select]

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Re^5: (OT) MySQL query to limit and sort
by rhesa (Vicar) on Feb 06, 2006 at 01:31 UTC

select id, url, images, Total
from (
    select *
    from temp
    order by id desc
    limit 10
) last10
order by Total desc;
[download]

  select Customers.name, sales.amount                     -- select na
+me and total amount spent. 
  from Customers, 
    (                                                     -- a sub-sel
+ect to find the 10 best buyers.
       select customer_id, sum(order_amount) as amount    -- This sele
+cts a column and an aggregate
       from Orders                                        -- from the 
+real table Orders.
       group by customer_id
       order by amount desc
       limit 10
  ) sales                                                 -- we name t
+his sub-select "sales".
  where sales.customer_id = Customers.id                  -- we INNER 
+JOIN the two "tables", 
                                                          -- so we can
+ cross-reference Orders against Customers.
[download]

As you can see, the "sales" sub-select isn't a real table in the database, but within this query we can treat it as if it were. We can select columns from it, and put extra constraints on it in a where clause. I hope it's a bit clearer now :)

[reply]
[d/l]
[select]