Re: [Firebird-devel] Updatable cursors are in need of some touchup

[Arno B. <fbd...@ab...>]

Hi,

>> > What you mean in "this is accordingly to the SQL specification"?
>> > AFAIR, the spec allows table aliases in UPDATE and DELETE.
>> 
>> In the spec, both UPDATE and FOR UPDATE contain a <column list>
>> syntactical element which is different from <column reference>.
> 
> What if in the FOR UPDATE OF <column list> the statement has a self
> referencing table JOIN and similarly named columns are repeated?

If i understand correctly in the standard only 1 table is allowed and indeed as Dmitry said no alias is allowed.
But i see no problem in adding alias support, because it is "something extra" to the standard. 
Previously (before SQL200n) the alias/correlation name in the update was also not allowed:
Before SQL200n: "UPDATE <table name> SET ..." was 
SQL200n and beyond: "UPDATE <table name> [[AS] <correlation name>] SET ..."
 
I'm not sure if it was in the final SQL2003 or in the next version, but in the most recent drafts. The alias is there.

> I much prefer the <column reference> because it allows the table alias to be
> taken into consideration which helps to distinguish which relation a column
> is a part of.
> 
> Isn't it true that <column list> is a subset of <column reference>?

No, but i don't see a problem in using <column reference> here.
 
> Also, isn't it possible that a <column list> is actually a list of
> individual <column reference> items?

No.

Regards,
Arno Brinkman
ABVisie

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