Re: Extending SQL a bit

Kim,

The expression (CURRENT_TIMESTAMP + 10000) will evaluate to NULL.  You 
can not use the addition operator with a timestamp.  As I see it there 
are two options.  Either create a new function that returns a timestamp 
given the appropriate input (eg. TIME_AFTER_NOW(1000) ), or change the 
EXPIRES grammar so it looks something like 'EXPIRES = 5 DAYS' and 
evaluate the '5 DAYS' part in Insert.java.

Toby.


Kim Schulz wrote:
> On Thu, 24 Feb 2005 14:36:42 -0800
> Tobias Downer <[email protected]> wrote:
> 
> 
>>As well as changing the grammar rules, you will also need to add the 
>>appropriate behaviour in com/mckoi/database/interpret/Insert.java to 
>>handle the information.
>>
>>Your grammar should probably look something like,
>>
>>   Expression time_exp = null;
>>   ...
>>      (   [ "(" BasicColumnList(col_list) ")" ]
>>             (   <VALUES> InsertDataList(data_list)
>>                     { type = "from_values"; }
>>               | select = Select()
>>                     { type = "from_select"; }
>>             )
>>         | <SET> AssignmentList(assignments) { type = "from_set"; }
>>      )
>>      [ <EXPIRES> <ASSIGNMENT> time_exp = DoExpression()
>>                     { cmd.putObject("expires", timp_exp); } ]
>>
>>This will create an 'expires' entry in the cmd object if the expires 
>>assignment is optionally given.  The expires object will be an
>>Expression.
>>
>>In com/mckoi/database/interpret/Insert.java, you would evaluate the 
>>expires expression if it's present and insert the data into your
>>hidden  column.
> 
> 
> This worked almost perfectly, but I have a problem when I want to do
> somthing else than EXPIRES=CURRENT_TIMESTAMP;
> 
> I would like to do somthing like CURRENT_TIMESTAMP+10000; but that just
> gives me an empty element in my hidden column. 
> 
> I thought that DoExpression() evaluated the expression
> CURRENT_TIMESTAMP+1000 to somthing useful or trew me an error. 
> 
> 
> in mysql I would do somthing like NOW()+1000 but NOW is not in the
> standard and I cant figure out whether it is possible to actually add
> 1000 to a TIMESTAMP in mckoi... is it possible? 
> 
> 
> 
> 
> 



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