https://bugzilla.wikimedia.org/show_bug.cgi?id=164
--- Comment #144 from Philippe Verdy <[email protected]> 2009-11-19 18:12:31 UTC --- Note that in SQL, the ORDER BY clause needs NOT unique sort keys. Not even for sort stability, because the SQL engine will ensure the sort stability itself from the default store order in the index (when there's a qualifying index for this sort order), or from the implicit positional "rowID's" automatically for each SELECT'ed row added to the temporarily created table/index during the query execution. Some SQL engines (like Oracle, Sybase, Informix, but probably not all index formats supported in various versions of MySQL) also store the rowID's of the component tables from which columns are extracted in the SELECT clause, in order to allow the columns under the read cursor to be updatable, but won't do that for columns computed from expressions, which are not updatable. This just requires opening the cursor "FOR UPDATE" (and sometimes, you can also limit the list of table columns that need to be updated within the cursor loop, which remains open during the transaction, in order to minimize the extra storage for dependant rowID's). -- Configure bugmail: https://bugzilla.wikimedia.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. _______________________________________________ Wikibugs-l mailing list [email protected] https://lists.wikimedia.org/mailman/listinfo/wikibugs-l
