Re: varchar vs varchar2

Jack wrote:

> <Quotes from documentation>
> The VARCHAR datatype is synonymous with the VARCHAR2 datatype. To avoid
> possible changes in behavior, always use the VARCHAR2 datatype to store
> variable-length character strings.
>
> </Quotes>
>
> I wonder what "possible changes in behavior" could be?
>
> Thanks.

Buried in the old documentation it states that the varchar and varchar2 could differ in trailing-blank/null comparison semantics in the future. For now 'varchar' seems to be converted consistently to 'varchar2', but at some future date comparing (varchar 'XYZ' to char 'XYZ ') might work differently from (varchar2 'XYZ' to char 'XYZ ')

For a fascinating look at the evolution (and the justification for not having thrown out my old manuals):

From my Oracle 5.1 Database Administrator's Guide

• CHAR datatype is stored in variuable length strings .... trailing blanks are not stored unless they are explicitly used inside quoted strings in the INSERT statement [there was not VARCHAR]

From my Oracle 6.0 Database Administrator's Guide

• The CHAR and VARCHAR datatypes are equivalent. .... While CHAR and VARCHAR are treated equally in Version 6.0, it is expected that in a future version of the ORACLE RDBMS, CHAR data will be fixed-length [both limited to 255 char]

From my Oracle 7.0 Concepts Guide

• (under VARCHAR2) Oracle compares VARCHAR2 values using the non–padded comparison semantics. See Oracle7 Server SQL Reference for more information on comparison semantics.
  • (under VARCHAR) The VARCHAR datatype is currently synonymous with the VARCHAR2 datatype. However, in a future version of Oracle, the VARCHAR datatype might store variable–length character strings compared with different comparison semantics. Therefore, use the VARCHAR2 datatype to store variable–length character strings.

and

"ANSI SQL Datatype: CHARACTER VARYING(n), CHAR VARYING(n) correspond to Oracle datatype VARCHAR(n)"

whereas

"DB2 or SQL/DS Datatype: VARCHAR (n) correspond to Oracle Datatype: VARCHAR2 (n)" Received on Mon Aug 04 2003 - 20:14:12 CDT