varchar data type question

HI, A customer use ESQL/C to write the application, they want to change some data type from char to varchar, the customer want to know whether the running result will be changed ? What's the internal difference between char and varchar data type with ESQL/C? thanks for your time.

From the esql/c side there is no difference between a char and a varchar. You write the esql/c program with the data being defined as a char[x+1] where 'x' is the max size that the varchar is defined to be. Of course the "+1" is to provide space for the null terminator. When the data is moved from the database to/from the esql/c program, it will automatically converted into the target definition. Madison Pruet Retired and Loving it On Thursday, July 13, 2017 8:47 AM, CHUAN LU <luchuan@cn.ibm.com> wrote: HI, A customer use ESQL/C to write the application, they want to change some data type from char to varchar, the customer want to know whether the running result will be changed ? What's the internal difference between char and varchar data type with ESQL/C? thanks for your time. ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum.

On Thu, Jul 13, 2017 at 7:46 AM, CHUAN LU <luchuan@cn.ibm.com> wrote: > A customer use > ​s​ > ESQL/C to write the application > ​. They want to change some data > type > ​s​ > from char to varchar, > ​and ​ > the customer want > ​s​ > to know whether the running > result will be changed? > ​It depends in part on how the ESQL/C is written. However, if it uses the CHAR data type (rather than say the string data type), then it is possible that you'll get blank padding on the strings​, which moots one of the main benefits of using VARCHAR. OTOH, it will continue to work without recompilation. > What's the internal difference between char and varchar data type with > ESQL/C? > ​Primarily that SQL and ESQL/C don't blank pad VARCHAR data. On disk, there's a byte stored for the length of the VARCHAR; that doesn't translate to the in-memory representation which is essentially the same as CHAR. ​ -- Jonathan Leffler <jonathan.leffler@gmail.com> #include <disclaimer.h> Guardian of DBD::Informix - v2015.1101 - http://dbi.perl.org "Blessed are we who can laugh at ourselves, for we shall never cease to be amused."

What is the reason to change a char for a varchar? If the column(s) are indexed be careful with the change... I assume the only valid reason for the change would be to save some space... but that comes with a cost, specially if the data is indexed. Regards On Thu, Jul 13, 2017 at 3:46 PM, CHUAN LU <luchuan@cn.ibm.com> wrote: > HI, > > A customer use ESQL/C to write the application, they want to change some > data > type from char to varchar, the customer want to know whether the running > result will be changed ? > > What's the internal difference between char and varchar data type with > ESQL/C? > > thanks for your time. > > > ************************************************************ > ******************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > -- Fernando Nunes Portugal http://informix-technology.blogspot.com My email works... but I don't check it frequently...