On Wed, 09 Jan 2008 10:54:21 -0500 Tom Lane <[EMAIL PROTECTED]> wrote:
> Alvaro Herrera <[EMAIL PROTECTED]> writes: > > Josh Harrison escribió: > >> Fine. I can use order by when I want to order it in terms of > >> some columns. But What if I want to maintain the same order as > >> in the database1? ie., I want my rows of TableABC in Database2 > >> to be the same order as the rows in TableABC in Database 1 ??? > > > You can't. > > According to the SQL standard, a table is an *unordered* collection > of rows, and the results of any query are produced in an > unspecified order (unless you use ORDER BY). The ambiguity about > row ordering is intentional and is exploited by most DBMSes > including Postgres to improve implementation efficiency. If you > assume there is such a thing as a specific ordering within a table, > you'll live to regret it eventually. Does it make any sense *knowing* how the implementation works to load records in a table in a specific order to improve performances? And yeah I know that once you start deleting/updating row you may lose the advantage you gained betting on some peculiarity of the implementation... but in case you're dealing with a mostly static table? eg. if I'm importing a table does it make any sense to pre-sort it before importing it in postgres? -- Ivan Sergio Borgonovo http://www.webthatworks.it ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
