Re: [libreoffice-users] Other SQL question as it affects Base

On 07/28/2012 03:36 PM, Dan wrote:
>      An example of an inner join:
> "table1" INNER JOIN "table2" ON "table1"."foreign 
> key"="table2"."primary key"
>
>      Mathematically the following seems to be possible:
> "table1" INNER JOIN "table2" ON "table1"."foreign 
> key"=2*"table2"."primary key"
>
>     Is the latter also an INNER JOIN? There seems to be other possible 
> multipliers other than 2. Also, what about inequalities? For example, 
> wanting to see all the rows of data for which the foreign key is less 
> than the MAX, MIN, or Ave of the primary key. (These are three 
> suggested "ON expressions" for an INNER JOIN. Using greater than 
> rather than less than is another possibility.)
>
>      I'm curious since I have a mathematical background. Any ideas?
>
> --Dan
Dan

If understand the keys they are not required to be integers though they 
usually are. The major requirement for a key is that it is unique and 
only exist once in the table. Keys can include multiple columns.  So 
multiplying a key would often not make sense. I believe you can add more 
requirements in the ON clause.

The reason keys are often integers is that one often defines the key as 
integer with automatic incrementing when a new row is added.

--
Jay Lozier
jslozier@gmail.com


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