> i was wondering, is there a difference in declaring a column as the primary > key vs. just declaring it as an index? Does a primary key go faster in > lookups than an index?
If you declare a primary key it will cause a unique index to be created on the column(s) you specify. A primary key is different from a regular index in that a regular index allows duplicates and NULLs. You can explicitly make an index UNIQUE and enforce a NOT NULL constraint on its column(s) in which case the index is similar to a primary key. There should not be any speed difference between a primary key and a not null unique index. Usually, a primary key is used when you are setting up a primary/foreign key relationship, but I believe R:Base allows you to specify that a foreign key references a unique index as well as a primary key. -- Larry --- RBASE-L ================================================ TO POST A MESSAGE TO ALL MEMBERS: Send a plain text email to [email protected] (Don't use any of these words as your Subject: INTRO, SUBSCRIBE, UNSUBSCRIBE, SEARCH, REMOVE, SUSPEND, RESUME, DIGEST, RESEND, HELP) ================================================ TO SEE MESSAGE POSTING GUIDELINES: Send a plain text email to [email protected] In the message SUBJECT, put just one word: INTRO ================================================ TO UNSUBSCRIBE: Send a plain text email to [email protected] In the message SUBJECT, put just one word: UNSUBSCRIBE ================================================ TO SEARCH ARCHIVES: Send a plain text email to [email protected] In the message SUBJECT, put just one word: SEARCH-n (where n is the number of days). In the message body, place any text to search for. ================================================
