MargaretGillon@xxxxxxxxxxxxxx wrote:
I am wondering what the limit is on the number of joins in a View or a
Select.
Background: I have many tables with similar flags such as Active,
Inactive, High, Medium, Low. I am storing the flags in a flag table and
then putting an int4 foreign key to the flag in the data tables. Some data
tables may have up to 15 flags, as well as 30 or 40 other foreign keys.
They're all left outer joins. Is this a problem for a view?
No real problem, but I suspect you'd be better off with a simpler setup:
CREATE TABLE has_some_flags(
...
priority_flag char,
...
CONSTRAINT valid_priority_flag CHECK
(priority_flag IN ('A','I','H','M','L'))
)
Or, perhaps better for your particular case:
CREATE DOMAIN priority_flag char
CONSTRAINT valid_pri_flag CHECK (VALUE IN ('A','I','H','M','L'));
CREATE TABLE has_flags(pri_flag priority_flag);
The main question would be whether your flags are going to change - if
not, they're more like a type and use the CHECK constraint. On the other
hand, if you're updating them regularly then you'll want to use joins.
--
Richard Huxton
Archonet Ltd
