Re: Index Creation Questions

Mark D. Stock wrote: >Schultheis, Carol L wrote: >> >> Can someone answer some basic general questions? >> >> 1. what is the difference between creating a unique index on a column >> via the create unique index statement >> versus using the primary key constraint when creating the table. > >The second one creates a unique index AND allows you to use referential >integrity. > Sorry, IMHO the UNIQUE INDEX _allows_ using of foreign keys on it. The difference is that PRIMARY KEYs don't allow the columns with NULL's. May be I'm wrong. >> 2. what is the difference between creating an index on a column via the >> create index statement >> versus using the alter table and adding a foreign key constraint.> >The second one creates an index AND implements automatic referential >integrity. > >> 3. what does the dbexport/dbimport facility do when indices are created >> by using constraints versus >> the create index statement, specifically when the dbimport creates >> the table, is the data then loaded >> before the constraints create the index??????? > >All constraints are created using ALTER TABLE statements AFTER the data >is loaded into the table. > >Hope that helps, >-- >Mark. > >+----------------------------------------------------------+-----------+ >|Mark D. Stock - Informix SA http://www.informix.com |//////// /| >|mailto:mdstock@informix.com http://www.informix.com/idn |///// / //| >|http://www.iiug.org +-----------------------------------+//// / ///| >| Tel: +27 11 807 0313 |If it's slow, the users complain. |/// / ////| >| Fax: +27 11 807 2594 |If it's fast, the users keep quiet.|// / /////| >|Cell: +27 83 250 2325 |Therefore, "No news: travels fast"!|/ ////////| >+----------------------+-----------------------------------+-----------+ -- Octav Chiriac Phone: (373) 2 21 20 96 NetInfo S.R.L. Fax: (373) 2 21 20 96 Chisinau (373) 2 24 00 83 Moldova, Republic of mailto:com@netinfo.moldova.net