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Re: check constraint question

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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.

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