Re: [boost] Interest in an ODBC library?

From: Hajo Kirchhoff (mailinglists_at_[hidden])
Date: 2005-07-27 07:52:43

Hi,

> What I don't like in your approach is that you require that there is a 
> type (my_table above) for each different rowset traversal "profile" - 

I don't. This is not required, this is merely an example. For small 
tables and simple queries its the fastest way. But not the only way.

> interested in only some of the columns - from 2 to 5, typically. Do you 
> require that the application always retrieves all columns?

Absolutely not.

odbc::statement s("SELECT column1,column2,etc... FROM ...");

is supported of course.

> Just imagine a single table with 4 columns - there are 15 different 
> subsets of columns there (not counting the queries with no columns). 

Also there does not have to be a 1:1 relationship between the members in 
my_table and the columns of the table. Subsets are fine. In fact, if you 
have a table with 150 columns and want to select only a subset of 
columns, you have a couple of options with my approach.

a) write a struct ... containing only a few member variables for those 
columns you want to select.

b) use individual variables to bind them.

c) all of the above

Another example:

odbc::statement s("SELECT one([bindto]a), two([bindto b), sixteen, 
seventeen, eighteen FROM huge_table");
long a, b;
struct some_struct;	// has members m_sixteen, ...
some_struct data;

s.bind(a, "a");		// bind variable a to column one
s.bind(b, "b");		// bind variable b to column b
        // bind all member variables of 'data' to columns
        // of the same name ... if they exist
s.bind(data);

> You does your approach scale in this aspect?

It does.
> 
> In my humble opinion, a DB library needs to be usable also with the 
> assumption that each query in a program can potentially retrieve a 
> *different* set of attributes (columns).

Absolutely.

  > http://soci.sourceforge.net/

Interesting approach. I'll probably steal ideas from it.

Thanks for your comments

Hajo

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