Re: Primary Key...Is One Required?

Bonnie Annelin wrote: > > I have a question regarding primary keys for tables. Is it necessary to > have a primary key for a table? According to Informix Documentation, > if a primary key does not exist for a table, a primary key is composed > of all columns taken together. Does this mean that Informix > automatically generates a primary key? I do a database dump (dbschema) > and do not see a primary key listed for my table. Also, I recently > attended an Informix Class where the instructor said that Informix does > not automatically generate a primary key. I'm now wondering whether > or not I should create a serial record_num primary key for this table > because if one is automatically generated out of every column (I have a > large number of columns) and because primary keys are automatically > indexed, this will be a very large/inefficient index. > > Thanks, > Bonnie Annelin Informix does not, to the best of my knowledge, automatically generate a primary key, nor do you need one unless you wish to enforce referential integrity. Informix does, however, automatically create a unique "rowid" for each row in a table. This column does not appear in a table schema but can be "selected" in a SQL statement eg select rowid from table. Hope this helps Gary Child