Thread: "order by" days of the week
Hello,
I am storing a schedule of services in a restaurant database (e.g.
breakfast, lunch...), and want to be able to order the results by the day
of the week. The table is as follows.
Table "schedule"
Column | Type | Modifiers
-------------+------------------------+-----------
business_id | integer | not null
day | character varying(20) |
start | time without time zone |
finish | time without time zone |
service | character varying(30) |
The day collumn will hold the days of the week "Monday", "Tuesday"... etc.
When I retrieve the data, I want to be able to sort by the days in
cronological order rather than in alphabetic order.
My questions are these:
1) Is it possible to use "order by" in conjunction with a list of strings
to tell it how to order the results?
2)Is there a way to store days of the week that is better than simply
using varchar and performing a check. I read about the time data formats
and they all seem to be more applicable to absolute times rather than
simply a day of the week. I also thought about storing the days as a
number between 1 and 7 then converting for display (1=Monday,
2=Tuesday...), but that didn't feel clean to me.
Any suggestions?
Thanks,
Doug
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On Sat, 2002-09-28 at 02:36, D. A. wrote:
> I am storing a schedule of services in a restaurant database (e.g.
> breakfast, lunch...), and want to be able to order the results by the day
> of the week. The table is as follows.
>
> Table "schedule"
> Column | Type | Modifiers
> -------------+------------------------+-----------
> business_id | integer | not null
> day | character varying(20) |
> start | time without time zone |
> finish | time without time zone |
> service | character varying(30) |
>
> The day collumn will hold the days of the week "Monday", "Tuesday"... etc.
> When I retrieve the data, I want to be able to sort by the days in
> cronological order rather than in alphabetic order.
>
> My questions are these:
> 1) Is it possible to use "order by" in conjunction with a list of strings
> to tell it how to order the results?
You could write a function to convert day names into numbers and sort on
the output of that function.
> 2)Is there a way to store days of the week that is better than simply
> using varchar and performing a check. I read about the time data formats
> and they all seem to be more applicable to absolute times rather than
> simply a day of the week. I also thought about storing the days as a
> number between 1 and 7 then converting for display (1=Monday,
> 2=Tuesday...), but that didn't feel clean to me.
It seems cleaner to me. It would take less storage and be easier to
validate ("CONSTRAINT "valid day" CHECK (day >= 0 AND day < 7)").
Create a view that has an additional dayname column defined as "CASE
WHEN day = 0 THEN "Sunday" WHEN day = 1 THEN "Monday" ... END" Then you
can sort by day but select dayname.
--
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Isle of Wight, UK
http://www.lfix.co.uk/oliver
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>>>>> "D" == D A <lameije@yahoo.com> writes:
D> 2)Is there a way to store days of the week that is better than simply
D> using varchar and performing a check. I read about the time data formats
D> and they all seem to be more applicable to absolute times rather than
D> simply a day of the week. I also thought about storing the days as a
D> number between 1 and 7 then converting for display (1=Monday,
D> 2=Tuesday...), but that didn't feel clean to me.
The was I've seen this done is to have an extra lookup table where
1=Monday does the translation between the key (the value 1) and the
human-readable version (the value "Monday"). I've not seen it for
this particular case (days of the week), but the idea is quite
general and works fine for this case.
roland
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