Re: Timestamp Column.

On Wed, 29 Apr 1998 13:40:36 -0400, "Art S. Kagel" <kagel@bloomberg.com> wrote: >pedrocr@dicoruna.es wrote: >> >> Hi all. >> >> I want to add a column of type timestamp in a table. (Informix Online 7.1) >> It's posible? >> In the manual i don't find the data type timestamp. >> Is there a type timestamp? >> How can i do? >> Please help. >> Thanks. > >Informix does not support type TIMESTAMP. You can use DATETIME along >with a DEFAULT constraint and an UPDATE TRIGGER to implement >automatically maintained timestamps. Try: > >create table mytable (>... >timestamp DATETIME YEAR TO FRACTION(3) DEFAULT CURRENT, >... >); > >Art S. Kagel You would have to set USEOSTIME or something like that in your config file for this to work. Question: Is fraction(3) enough to avoide two updates getting the same timestamp value? May be it would be possible to device a system with timestamp as an integer that is increased by 1 for every update? I haven't thought it through, but it may require more support in the application than would be desirable. If you want to use the timestamp for optimistic locking (isn't that what it's ususally used for) an alternative is to update with a where clause that includes all fields in the table (or all fields to be updated) with their value at the time the row was read by the application. That's not too hard to implement depending on the language you use. Nils Myklebust NM Data AS Norway E-mail: Nils.Myklebust@nmdata.com FAQ at: http://www.iiug.org/techinfo/faq/faq_top.html (Now with ODBC info under "Third party products".)