Re: Need schema design advice

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От Ben Chobot
Тема Re: Need schema design advice
Дата
Msg-id 01074800-FA61-403A-A9D7-FD645A2E8958@silentmedia.com
обсуждение исходный текст
Ответ на Re: Need schema design advice  (Martin Gainty <mgainty@hotmail.com>)
Ответы Re: Need schema design advice
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On Oct 12, 2008, at 5:51 PM, Martin Gainty wrote:

could you provide a brief explanation of EAV ?


Instead of:

create table vehicles
(
kind text primary key,
wheels int
);
insert into vehicles (kind, wheels) values ('car',4);
insert into vehicles (kind, wheels) values ('bike',2);

create table boats
(
kind text primary key,
displacement int
);
insert into boats (kind,displacement) values ('small boat',1000);
insert into boats (kind,displacement) values ('big boat',300000);



... in an EAV model you would do something like:

create table eav
(
kind text primary key,
attr text,
value text
);
insert into eav (kind, attr, value) values ('car','wheels','4');
insert into eav (kind, attr, value) values ('bike','wheels','2');
insert into eav (kind, attr, value) values ('small boat','displacement','1000');
insert into eav (kind, attr, value) values ('big boat','displacement','300000');




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