[SQL] some howto/theory book/tutorial on practical problem solving in SQL
I'm looking to some book/tutorial/sample code that will teach me how to use SQL to solve some standard problem that goes a bit beyond using group by and aggregates. Something like "SQL problem solving" or "SQL design strategies for selected problems". My current problem is how to manage discounts in SQL, inside transactions. Specifically how to "delete" promotions if they are overlapping, considering I have to display discounted prices on a 1M article DB and I may have hundreds of promotions running and they may involve even 10% of the catalogue. But this is just the beginning. I bet I'll have different set of problems later. Online tutorial/howto or reference to Open Source programs that really exploit SQL (and not python, php, ruby) to deal with discounts would be very welcome. eg. I did find very educational to look in the code of GNUMed in the past. Actually a reference to some Open Source software that does discount management at the DB level would be a very good pointer. And of course I'm using postgresql and even if DB agnostic techniques will be welcome I don't need to be DB neutral, I'm working on postgresql. I skimmed through Celko books and at the moment they seems the nearest thing to what I'd like to learn even if too much "theoretical" at the moment. O'Reilly "SQL cookbook" is another example of the kind of stuff I'm looking for... but the examples are more like ingredients then recipes. thanks -- Ivan Sergio Borgonovo http://www.webthatworks.it -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
Re: [SQL] some howto/theory book/tutorial on practical problem solving in SQL
On Sun, Jan 11, 2009 at 9:32 AM, Ivan Sergio Borgonovo wrote: > > My current problem is how to manage discounts in SQL, inside > transactions. Specifically how to "delete" promotions if they are > overlapping, considering I have to display discounted prices on a 1M > article DB and I may have hundreds of promotions running and they > may involve even 10% of the catalogue. But this is just the > beginning. > > I bet I'll have different set of problems later. Well, if you can't find a book that deals with it, I'm betting someone on the list will understand the issue and help out. :) > I skimmed through Celko books and at the moment they seems the > nearest thing to what I'd like to learn even if too much > "theoretical" at the moment. O'Reilly "SQL cookbook" is another > example of the kind of stuff I'm looking for... but the examples are > more like ingredients then recipes. I highly recommend Celko's SQL books. They may seem too theoretical, but they have a lot of good information I found myself reusing all the time when I first started out. I was a little disconcerted by his resemblence to Anton Lavie (sp) at first though. -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
[SQL] Seeking for the fore-part of the key
Hi, Let's assume I have a table (called tbl) with a column 'name' and an index on it. How to optimally find records whose name column begins with - say - "Pre"? I know it can be done with LIKE (WHERE name LIKE 'Pre%'), but will this use the index mentioned above to optimize the search? Thanks, Otto
Re: [SQL] Seeking for the fore-part of the key
Havasvölgyi Ottó schrieb:
> Hi,
>
> Let's assume I have a table (called tbl) with a column 'name' and an index on
> it.
> How to optimally find records whose name column begins with - say - "Pre"?
> I know it can be done with LIKE (WHERE name LIKE 'Pre%'), but will this use
> the
> index mentioned above to optimize the search?
for instance:
test=*# \d words
Tabelle »public.words«
Spalte | Typ | Attribute
+--+---
w | text |
Indexe:
»idx_words_w« btree (lower(w) text_pattern_ops)
test=*# explain analyse select * from words where lower(w) like lower('foo%');
QUERY PLAN
Bitmap Heap Scan on words (cost=40.65..1779.81 rows=1595 width=13) (actual
time=0.021..0.021 rows=0 loops=1)
Filter: (lower(w) ~~ 'foo%'::text)
-> Bitmap Index Scan on idx_words_w (cost=0.00..40.25 rows=1595 width=0)
(actual time=0.019..0.019 rows=0 loops=1)
Index Cond: ((lower(w) ~>=~ 'foo'::text) AND (lower(w) ~<~
'fop'::text))
Total runtime: 0.047 ms
(5 Zeilen)
Andreas
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Re: [SQL] some howto/theory book/tutorial on practical problem solving in SQL
On Sun, 11 Jan 2009 11:19:19 -0700 "Scott Marlowe" wrote: > On Sun, Jan 11, 2009 at 9:32 AM, Ivan Sergio Borgonovo > wrote: > > My current problem is how to manage discounts in SQL, inside > > transactions. Specifically how to "delete" promotions if they are > > overlapping, considering I have to display discounted prices on > > a 1M article DB and I may have hundreds of promotions running > > and they may involve even 10% of the catalogue. But this is just > > the beginning. > > I skimmed through Celko books and at the moment they seems the > > nearest thing to what I'd like to learn even if too much > > "theoretical" at the moment. O'Reilly "SQL cookbook" is another > > example of the kind of stuff I'm looking for... but the examples > > are more like ingredients then recipes. > I highly recommend Celko's SQL books. They may seem too > theoretical, but they have a lot of good information I found > myself reusing all the time when I first started out. I was a OK... let's be more clear... they seems the books I'd surely read if I had 1 month to find a proper solution to my problems and become a better programmers for the years to come. Actually from a quick glance they are definitively more practical than a book on sets algebra ;) and among all the books I had a chance to skim they really look the ones that could be useful and they have a good chance to find a permanent place in my bookshelf. Just not to misguide people. If I had other 3 months I'd pick up Date's book. I just remember now I gave a look to a .*postgres.*ecommerce book but while it seems to me it could be a good book for learning some practical postgresql and start to know the tool it was not the kind of book that I'd title "how to solve this in SQL". I just saw there is a "Sql Puzzles" by Celko that looks promising. I was able to see the first 2 puzzles on Google books. Now I'm downloading all the Open Source ecommerce apps I could find... but having done this before I think none of them will really exploit the DB and will rely mostly on php. I think Open Source accounting [1] programs may have more chances to teach me something about the problem I'd like to solve since they tend to be less mysqlish. If anyone know an accounting Open Source program that really exploit postgresql as an engine I'd be glad to look at the source. > little disconcerted by his resemblence to Anton Lavie (sp) at > first though. http://images.google.com/images?q=Joe+Celko http://en.wikipedia.org/wiki/Anton_Szandor_LaVey I think I'm going to read some Teach yourself SQL in 1fs by Laura Lemay if I want to keep sleeping at night or I may enrol myself in Milingo's army. If I had eternity I wouldn't be so worried about performances so I think I could finish War and Peace. I just found an answer by Celko to a problem similar to mine here: http://www.eggheadcafe.com/software/aspnet/31256828/calculate-discount-by-cat.aspx [1] accounting? just a tool that deals with discounts and an inventory. What would be the right term to search for in google? -- Ivan Sergio Borgonovo http://www.webthatworks.it -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
