Re: unique constraint on 2 columns

[Jonathan Vanasco <postgres(at)2xlp(dot)com>]

On Apr 20, 2007, at 5:43 PM, Vladimir Zelinski wrote:

> This looks like more table design problem than
> database limitation.
> The one column should accommodate values from both
> columns with unique index built on this column. Your
> requirements tell me that these values are the same
> nature and should be placed in the same column. To
> distinguish between them use another column to put an
> attribute.

No, both values can be present at once.  They're both external facing  
guids that point to the same resource and serve as keys for the table  
data.  Some rows have one, some have two.

in regards to  table desgin solution, if I redid anything it would be  
something like:
	table_main
		main_id
	table_main_2_guid
		main_id
		guid_id	unique
		context_id

but then i'm using 2 tables and have to join -- which means I need to  
rewrite evertyhing that queries this table - which is both  the core  
table for my application and supposed to be free of any multi-table  
queries for simple reads.

so i'm going to try the trigger route.


// Jonathan Vanasco

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