[thelist] DB "Limit" Command Question

[Nick Brogna]

Sloppy, quick example...

SELECT field1,field2 FROM table ORDER BY field1 ASC LIMIT 20;

You can (loosely) break down the order of operations in the above  
query like so:
  	- Get all the contents of columns field1 and field2 from the table  
"table"
	- Sort our newly obtainted dataset by the value of field1 (lowest to  
highest)
	- limit our dataset to be returned by the query to the first 20  
records in the newly sorted dataset and return those.

Cheers,
Nick Brogna

On Apr 16, 2009, at 11:18 AM, Luther, Ron wrote:

> Hi Gang,
>
> Okay, I'm pretty sure that if I run a query containing both a clause  
> to limit output to 20 records AND a clause to sort or order the data  
> in some way that the query will execute through the entire table  
> (data model) and then limit the output sent back to the viewport to  
> the 20 records I specified.
>
> But what if I don't?
>
> What if I run a 'select field1, field2, field3 from tableA' that  
> contains a 'limit output to 20 records" clause?
>
> Does it run through the whole table and then return 20 records?  Or  
> does it stop executing at 20 records and return?
>
> Quizzically,
> RonL.
>
> [Yeah, the answer might very well vary by DBMS.  Anybody got answers  
> for any popular DBs?]
>
>
> -- 
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