[Haskell-beginners] Ranges and List Comprehensions in SQL

[Toby Thain]

On 2-Sep-10, at 3:54 PM, Tom Murphy wrote:

> Hi Everyone,
>
>      Is there a "From SQL"-type function that "restores" a range or  
> list comprehension?
>
> Example:
> Let's say I want to keep track of which episodes of a TV show I've  
> seen. I have an SQL table, in which is a record:
>    id (INTEGER): 30
>    title (VARCHAR): "The Simpsons"
>    episodes_watched (Some data format): [1..4], [14], [18..21],  
> [23..25]

To model this relationally, episodes_watched cannot be some kind of  
composite value. You need two relations, for example:

CREATE TABLE tv_show (
	id INTEGER NOT NULL, -- etc
	title VARCHAR(80),
	PRIMARY KEY (id)
);
CREATE TABLE episodes_watched (
	tv_show_id INTEGER NOT NULL,
	episode_number INTEGER,
	PRIMARY KEY (tv_show_id, episode_number)
	-- and ideally a foreign key constraint
);

Data:

tv_show (30, "The Simpsons")
episodes_watched (30,1), (30,2), (30,3), (30,4), (30,14), (30,18),  
(30,19), (30,20), (30,21), (30,23), (30,24), (30,25)

--Toby


>
> Then, when I pull the record, in Haskell, the "Episodes Watched" is  
> already one list:
> [1,2,3,4,14,18,19,21,23,24,25]
>
> , or a series of lists that I can append together:
> [1,2,3,4], [14], [18,19,20,21], [23,24,25]
>
>
> Note in the example that I would like to be able to store multiple  
> ranges within a single record.
>
>
> Thanks so much for any help!
> Tom
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