[SQL] Re: Cascading Deletes
> 1. re_create your table set _ID as primary key This is not going to work unless a parent is prohibited from having more than one child. From the brief sample data supplied, this is clearly not the case. Join 18 million Eudora users by signing up for a free Eudora Web-Mail account at http://www.eudoramail.com
[SQL] Re: many-to-many mapping
Am I the only one who's nervous about these two tables referencing each other like this? I would have a concern that this is being imposed, perhaps, by some external format that the data arrives in, and that a decently normalized design will have a simple all-key table containing nothing but serial # id's from both primary tables. Join 18 million Eudora users by signing up for a free Eudora Web-Mail account at http://www.eudoramail.com
Re: [SQL] fetching rows
I hate to be the bearer of bad news, but if you're using PHP and you wanted to fetch just 25 rows at a time for a single page, and then fetch more when the user clicks on a NEXT button or link, you're completely out of luck. Each http transaction is completely separate and so you can't maintain a cursor between pages. Perhaps LIMIT would help you here; but I've found it more useful to make sure there is a unique key for the order I'm displaying, and then say "WHERE key > highest_key_value_on_current_page" Join 18 million Eudora users by signing up for a free Eudora Web-Mail account at http://www.eudoramail.com
RE: [SQL] INSERT [IGNORE] INTO TABLE
>Not a good feature for me. Me neither, but... >Check existence and then insert or update. At least once a week I seem to be responding to this exact same suggestion. Somebody _please_ tell me if I'm the only one in the whole world who worries about race conditions? What's wrong with just making sure there's a proper unique key, and then just inserting the row? The returned error message will tell you if a failure is due to duplicate key, missing non-null column, or an actual disaster. Join 18 million Eudora users by signing up for a free Eudora Web-Mail account at http://www.eudoramail.com
[SQL] Re: unique sequences
> Rather, each time you wish to do an insert, > query the existing data to see what the > maximum value is existing in the database. > Add 1 to that and use this as your new value. > This is guaranteed to not have any holes in > the sequence. True, but alas it _doesn't_ guarantee uniqueness, since there's nothing to prohibit 2 or more back ends getting the same max() at the same time... Thinking off the top of my head, I'm not sure you can apply FOR UPDATE to an aggregate function, so there's probably no solution there, either. Join 18 million Eudora users by signing up for a free Eudora Web-Mail account at http://www.eudoramail.com
[SQL] Re: Wildcard in date field
The suggest solution works:
> SELECT * FROM my_table WHERE
> date_part('month', col_name::datetime) = '06'
> AND date_part('year', col_name::datetime) =
> '2000';
But you can also just do a comparison:
where col_name >= '2000-06-01' AND col_name <= '2000-06-30'
Using the correct date format for your environment, of course.
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[SQL] Re: m4 macros plus PostgreSQL anyone?
No advice, just a big question: why M4? I've made great use of M4 myself for gluing a constant- and macro-defining capability to languages that don't have such (even Foxpro--no, no, please don't ask!) but in this day and age perl would be far more expressive and capable for the things you are trying to do, wouldn't it? Join 18 million Eudora users by signing up for a free Eudora Web-Mail account at http://www.eudoramail.com
