Thanks Larry! (: ----- Original Message ----- From: "Lawrence Lustig" <[EMAIL PROTECTED]> To: "RBASE-L Mailing List" <[email protected]> Sent: Monday, March 21, 2005 2:37 PM Subject: [RBASE-L] - Re: primary key vs index
> > 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. > ================================================ > --- 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. ================================================
