RE: Porting Guide and Statement made about Char Vs VarChar

["Wilt, Charles" <WiltC@xxxxxxxxxx>]

The Oracle porting guide has a similar statement:

"Many Oracle applications use the VARCHAR2 data type for very small character strings. In these
circumstances, it is better to port it to the fixed-length DB2 UDB data type CHAR(n), as it is more
efficient and takes less storage than the VARCHAR data type. The CHAR data type should always be used
for columns of 40 bytes or fewer."


Charles
 

> -----Original Message-----
> From: midrange-l-bounces@xxxxxxxxxxxx 
> [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Scott Johnson
> Sent: Tuesday, November 27, 2007 2:51 PM
> To: MIDRANGE-L@xxxxxxxxxxxx
> Subject: Porting Guide and Statement made about Char Vs VarChar
>
> http://www-03.ibm.com/servers/enable/site/db2/porting.html
>
> I have had a read thru the "DB2 for i5/OS porting guide: 
> MySQL to System i 
> platform" and found a very interesting statement made about 
> when to use 
> Char versus VarChar. Page 11 has this tidbit:
> "The CHAR data type must always be used for columns of 40 
> bytes or fewer."
>
> Why would IBM make such a strong statement that we use a Char 
> when the 
> field is less than 40 bytes in length?  Would it still be the 
> case when I 
> have a 35 character field that over 75% of the time only contains 15 
> characters?  What about a 10 character field that is mostly 
> only has data 
> that is 4 characters in length?  I realize that with a 
> VarChar there are 
> the bytes tacked on to contain the length, but I must be 
> missing something 
> someplace.
>
> Can someone with some deep dark knowledge of the internal 
> workings of DB2 
> for i5/OS give me some info on why IBM would say this.
>
> Thanks,
>     Scott
>
>
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