Обсуждение: char o varchar
Hoii!! I am creating my struct and I have the question : What I must use for character fields char or varchar? Which are the differences? and the better TIA *-------------------------------------------------------* *-Edwin Quijada *-Developer DataBase *-JQ Microsistemas *-809-747-2787 * " Si deseas lograr cosas excepcionales debes de hacer cosas fuera de lo comun" *-------------------------------------------------------* _________________________________________________________________ Charla con tus amigos en línea mediante MSN Messenger: http://messenger.yupimsn.com/
On Tue, 16 Sep 2003, Edwin Quijada wrote: > > > > > Hoii!! > > I am creating my struct and I have the question : > What I must use for character fields char or varchar? > Which are the differences? and the better Generally speaking, varchar or text() types are preferred. char() types are padded. I.e. if you create a table with char(8) and insert 'abc' then select it, you'll get 'abc ' back, i.e. abc followed by padding spaces to make it 8 wide. Most of the time this is not what the user wants.
As of my knowlege, varchar as the choice when you have varying lenght strings, because only the real string lenght is stored in the db, while char is usefull when most of your records ar exactly the stringlenght defined by the column, because no overhead is to be kept for storing the actual stringlenght. Regards Edwin Quijada wrote: > > > > > Hoii!! > > I am creating my struct and I have the question : > What I must use for character fields char or varchar? > Which are the differences? and the better > TIA > > *-------------------------------------------------------* > *-Edwin Quijada > *-Developer DataBase > *-JQ Microsistemas > *-809-747-2787 > * " Si deseas lograr cosas excepcionales debes de hacer cosas fuera de > lo comun" > *-------------------------------------------------------* > > _________________________________________________________________ > Charla con tus amigos en línea mediante MSN Messenger: > http://messenger.yupimsn.com/ > > > ---------------------------(end of broadcast)--------------------------- > TIP 8: explain analyze is your friend -- Andreas Fromm ----------------------------- Drink wet cement... ... and get stoned
On Wed, Sep 17, 2003 at 09:11:54AM +0200, Andreas Fromm wrote: > As of my knowlege, varchar as the choice when you have varying lenght > strings, because only the real string lenght is stored in the db, while > char is usefull when most of your records ar exactly the stringlenght > defined by the column, because no overhead is to be kept for storing the > actual stringlenght. No, the overhead is present for char(n) as well, because it stores the length in _bytes_ while the "n" is the length in characters; they could be different. -- Alvaro Herrera (<alvherre[a]dcc.uchile.cl>) One man's impedance mismatch is another man's layer of abstraction. (Lincoln Yeoh)