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Re: How to do the equivalent of 'describe' with a SELECT?

From: Ramon F Herrera <>
Date: 31 Mar 2007 11:22:11 -0700
Message-ID: <>

On Mar 31, 12:05 pm, wrote:
> On 31 Mar 2007 07:50:06 -0700, "Ramon F Herrera" <>
> wrote:
> >The SQL code that I need is for a Pro*C/C++ application. Before my
> >compiled C program does its main thing, it should check the current
> >sizes of the variables in the target table.
> Why, do you think you can dynamically change the change of variables
> of a *compiled* program? That would be very weird.
> >I would like to be able to change the variables' sizes, for instance,
> >from:
> >VARCHAR(20);
> >to
> >VARCHAR(30);
> >without having to recompile all my C programs. Or at least, reduce the
> >impact of such resize.
> >TIA,
> >-Ramon
> In PL/SQL you would declare the variable as
> <variable> <table>.<column>%type
> but you would still need to recompile everything (automagically).
> May be something similar exists in Pro*C.
> Apart from that your task is impossible: you simply can't change
> dynamically the limits of *statically* declared variables, or you
> would need pointer variables everywhere.
> Such is the fate of a developer hardcoding everything and not using
> constants.
> --
> Sybrand Bakker
> Senior Oracle DBA

This is the situation, Sybrand.

My application creates delimited <tablename>.dat files and I want to make sure that some fields are properly truncated (or perhaps there is a way to tell SQL*Loader to do the truncation? I rather do it myself, and spare sqlldr the trouble).

Currently the guy wearing the SQL/PL hat and the C developer hat is just me, but maybe later on, some guy will change the sizes of variables and break things.

I have some programs that read files from disk and place them in an array. The typical solution is to declare a huge array size which will hopefully never be outgrown.

I think this should be used:

 if (numberOfLines > MAXLINES) {
   printf("This program has to be recompiled\n");    printf("Change the value of `MAXLINES' to at least %d\n", numberOfLines);

   exit (99);

I am thinking of using a similar approach with the sizes of variables: allow the PL/SQL guy to change them anytime, without having to tell the C developer, who will find out about the change next time he tries to run one of his programs.

-Ramon Received on Sat Mar 31 2007 - 13:22:11 CDT

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