Re: char vs varchar ?

In article <3nr1c3$5so_at_maverick.tad.eds.com>, Bob Wuller (rew_at_sfsv.opr.eds.com) writes:
>In article <3n5vrf$bqo_at_cardinal.fs.com>, skannan_at_PROBLEM_WITH_INEWS_GATEWAY_FILE ( S. Kannan) says:
>>
>> Varchar and Varchar2 are currently synonymous. However Oracle Corporation
>> may change the way Varchar works, in a future version.
>>
>> The difference between char and varchar in Oracle 7 and above is that
>> char is fixed length and can store upto 255 characters. Varchar (or
>> Varchar2 currently) is variable length and can store upto 2000 bytes
>
>With Oracle 7, is their a performance decrease when using both fixed and varchar fields?
>
>We are designing a database using a CASE tool. We want to use both fixed and varchar fields
>because the database will be generated for both Oracle (on the workstation) and DB2
>(on the mainframe). DB2 runs faster with fixed fields than varchar fields.
>
>Now another group will access our database with other tools, including Oracle Forms.
>They want us to define all fields as varchar instead of our current design, which mixes
>fixed and varchar fields.

Hi Bob,

Asides from the fact that CHAR is a fixed length data_type, and will be right padded with spaces (As I am sure has been mentioned by many people), there is one crucial difference you may need to keep in mind.

If you use a CHAR data_type in a SQL*Forms 4 to 4.5 application, you cannot use that field to establish a relationship like Master-Detail.

It is the result of the way Forms creates the query. To see the difference, force an error condition in Forms, and then display the error.

I have queried this with Oracle, and they concur that it may be a problem under certain circumstances. It has not been changed for Forms 4.5 because it works they way it is supposed to, which is a pain in the a...neck.

Regards,
Alex Long

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