Re: check constraint question - Mailing list pgsql-general

On 04/08/2014 03:41 PM, Rob Sargent wrote:

On 04/08/2014 03:36 PM, CS_DBA wrote:

On 04/08/2014 03:31 PM, Rob Sargent wrote:

On 04/08/2014 03:26 PM, CS_DBA wrote:

On 04/08/2014 03:17 PM, Rob Sargent wrote:

On 04/08/2014 03:09 PM, CS_DBA wrote:

On 04/08/2014 02:58 PM, Rob Sargent wrote:

On 04/08/2014 02:51 PM, CS_DBA wrote:

Hi All

we have a table like so:


customer (
cust_id                     integer not null primary key,
cust_group_id          integer not null,
group_account_id    integer not null,
cust_name               varchar not null,

...
)

we want to force the cust_group_id to be unique across all group_account_id's but not necessarily across the entire table

I assume the best approach would be a check constraint yes? Will this be excessively poor per performance if the table gets big?

Thoughts?

Thanks in advance

A unique index on cust_group_id and group_account_id doesn't do it for you?

oh right! duh!   It's been one of those days....

Which column goes first depends on your lookup expectations.

Thanks!


Here's another one:


customer (
cust_id                     integer not null primary key,
cust_group_id          integer not null,
group_account_id    integer not null,
cust_name               varchar not null,
cust_template_id      integer,
...
)

If cust_template_id IS NOT NULL then it must reference a valid cust_id

Check constraint?

Nope. Useless column :).  You already have cust_id so cust_template_id is either null or already known.

Actually its a goofy design in the web app... users can enter the template_id on the fly and if they do we want to enforce the fact that it's a valid cust_id (meaning any existing cust_id can be used as a template but made up template ID's - meaning an id that does not match an existing cust_id should be disallowed)


Thoughts?

Really goofy. They could type in any valid cust_id, theirs or not theirs.
What are you after with template_id.  How would your app use it. Why would user fill it in?

Not sure yet (new client)... for now they simply want to force the template column to be a valid cust_id, if it is not null...  later I'll be digging into their design and pushing them to make some db architecture changes...