Hi all, If I do this:
select u, u, u from (select gen_uuid() u from rdb$database) ...I get three different UUID's. I would have expected the derived table to be evaluated once. The subquery returns a single row with one column. Selecting this column three times should get me three times the same value, IMO. The standard says about derived tables: 4.14.2 Types of tables (...) A derived table is a table derived directly or indirectly from one or more other tables by the evaluation of a <query expression> whose result has an element type that is a row type. The values of a derived table are derived from the values of the underlying tables when the <query expression> is evaluated. Although this is not 100% explicit, it suggests that the DT result set is determined only once. Executing <query expression> again and again for each column selected from the DT seems a waste of resources as well as a serious limitation of its usability with non-deterministic functions. The same goes for CTE's. So... have we implemented the DT and CTE features correctly? And if so, can somebody point me to some authoritative sources? Kind regards, Paul Vinkenoog ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
