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* checking data integrity in a recursive table
@ 2003-01-23 20:19 Luke Pascoe <luke.p@kmg.co.nz>
0 siblings, 1 reply; 2+ messages in thread
From: Luke Pascoe @ 2003-01-23 20:19 UTC (permalink / raw)
To: pgsql-sql
Hi, I have a table that references itself to create a tree-like structure,
eg:
CREATE TABLE tree (
id SERIAL NOT NULL,
name VARCHAR(255) NOT NULL,
parent INT NULL,
customer IN NOT NULL,
CONSTRAINT parent_key...
CONSTRAINT customer_fk FOREIGN KEY (customer) REFERENCES customer
);
ALTER TABLE tree ADD CONSTRAINT FOREIGN KEY (parent) REFERENCES tree;
As you can see tree also references the customer table.
What I need is a CHECK that will ensuer that any given "tree" row has the
same customer as its parent.
Remember that "parent" can also be NULL.
Or would this be better done as a trigger?
TIA!
========================================
Luke Pascoe
KMG (NZ) Limited. http://www.kmg.co.nz
Mobile: (021) 303019
Email: luke.p@kmg.co.nz
========================================
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: checking data integrity in a recursive table
@ 2003-01-31 05:32 Bruce Momjian <pgman@candle.pha.pa.us>
parent: Luke Pascoe <luke.p@kmg.co.nz>
0 siblings, 0 replies; 2+ messages in thread
From: Bruce Momjian @ 2003-01-31 05:32 UTC (permalink / raw)
To: Luke Pascoe <luke.p@kmg.co.nz>; +Cc: pgsql-sql
Luke Pascoe wrote:
> Hi, I have a table that references itself to create a tree-like structure,
> eg:
> CREATE TABLE tree (
> id SERIAL NOT NULL,
> name VARCHAR(255) NOT NULL,
> parent INT NULL,
> customer IN NOT NULL,
> CONSTRAINT parent_key...
> CONSTRAINT customer_fk FOREIGN KEY (customer) REFERENCES customer
> );
> ALTER TABLE tree ADD CONSTRAINT FOREIGN KEY (parent) REFERENCES tree;
>
> As you can see tree also references the customer table.
>
> What I need is a CHECK that will ensuer that any given "tree" row has the
> same customer as its parent.
> Remember that "parent" can also be NULL.
>
> Or would this be better done as a trigger?
Good question. I don't think you can do actualy SQL lookups in a CHECK.
I think you will need a trigger, either in pl/pgsql or in C using SPI to
issue the lookup queries.
You can have a CHECK clause that deals with multiple columns:
CREATE TABLE friend2 (
firstname CHAR(15),
lastname CHAR(20),
city CHAR(15),
state CHAR(2) CHECK (length(trim(state)) = 2),
age INTEGER CHECK (age >= 0),
gender CHAR(1) CHECK (gender IN ('M','F')),
last_met DATE CHECK (last_met BETWEEN '1950-01-01'
AND CURRENT_DATE),
CHECK (upper(trim(firstname)) != 'ED' OR
upper(trim(lastname)) != 'RIVERS')
);
However, that doesn't help you because you can't reference a column in
another row of the same table.
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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2003-01-23 20:19 checking data integrity in a recursive table Luke Pascoe <luke.p@kmg.co.nz>
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