Hi folks.
I'm trying to model a vehicle compound structure and have the following:
Four seperate compounds, North, East, South and West,
Each compound has a number of rows with Labels fastened to the fences
As the compounds are not perfect rectangles, the rows are of differing
lengths.
I have tables for the compounds and rows, but can't work out how to set the
constraints on the bays table - a seperate table while development takes
place, merged with our existing stock table eventually;
I've managed to add the constraint to prevent compound_bay records being
created for compound rows that do not exist,
My question is, how do I prevent a record being created for a bay higher than
than the length of the row, i.e. > 20 in North row A or > 40 in East row A?
-- list of available compounds
create table compounds ( co_id int4 primary key, co_name varchar(80)
);
-- description of rows per compound
create table compound_rows ( co_id int4 references compounds(co_id), cr_id int4 not null, cr_label
varchar(5)not null, cr_sequence int4 not null, cr_length int4, primary key (co_id, cr_id)
);
create unique index "compound_rows_sequence_index" on compound_rows using btree (co_id, cr_sequence);
create unique index "compound_rows_label_index" on compound_rows using btree (co_id, cr_label);
COPY compounds (co_id,co_name) from stdin;
1 North
2 East
3 South
4 West
\.
COPY compound_rows (co_id,cr_id,cr_label,cr_sequence,cr_length) from stdin;
1 1 A 10 20
1 2 B 20 20
1 3 C 30 25
1 4 D 40 25
2 1 A 10 40
2 2 B 20 40
2 3 C 30 45
2 4 D 40 45
\.
-- link from stock table one bay per vehicle
create table compound_bays ( st_VIN varchar(17) primary key references stock (st_VIN), co_id int4 not null,
cr_id int4 not null, cb_id int4 not null
);
alter table compound_bays add constraint compound_bays_row_check foreign key (co_id, cr_id) references
compound_rows(co_id,cr_id);
--
Gary Stainburn
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