NNDB's Not a Database

Introduction

NNDB is my playground for understanding databases.

It is a C++ library that provides in-memory data storage and retrieval using syntax that is intended to feel natural for C++/STL, but which also might feel slightly like SQL if you squint and pound the top of your head with a seminal programming textbook.

As part of NNBD I developed the ForEachType class template and contributed it to Loki. Follow the links to find out more.

Column types are fixed at compile-time and checked by the compiler.

Download

You can download it from the NNDB download page.

Examples

Example syntax:

 nndb::Table<std::string, int> my_table;

 my_table.Insert( nndb::Values<std::string, int>(
     "NNDB first row", 47 ) );

 nndb::ResultSet<std::string, int> result_set =
     nndb::Select<std::string, int>( nndb::select_star, my_table );

This does something sort of similar to the following SQL:

 CREATE TABLE my_table (
     col0 VARCHAR( ... ),
     col1 INT
 );

 INSERT INTO my_table( col0, col1 ) VALUES ( "NNDB first row", 47 );

 SELECT * FROM my_table;

You can use the results of your select like this:

 nndb::ResultSet<std::string, int>::const_iterator begin_it =
     result_set.begin();

 const nndb::Values<std::string, int>& first_row = *begin_it;

 assert( nndb::Field<0>( first_row ) == "NNDB first row" );
 assert( nndb::Field<1>( first_row ) == 47 );

To see all the current features in action, read the complete example.

(Lack of) features

Here are some useful features of databases that NNDB actually has (analogues of) now:

CREATE TABLE ...
INSERT INTO table VALUES( ... )
SELECT * FROM table
SELECT ... WHERE ...
SELECT ... ORDER BY ...
SELECT ... WHERE ... ORDER BY ...
Indexes (unique and not unique)

Here are some useful features of databases that NNDB might one day have:

SELECT col0, col1 ...
SELECT ... JOIN ...
Save/load to disk

Here are some useful features of databases that NNDB will never have:

Multiple simultaneous users
User security
Multiple processes

Discussion

The database definition is almost always known at compile time - so why not use the compiler to enforce type correctness?

Note there is no need for anything like a BLOB column type or similar in NNDB - any type that is a value type (i.e. may be copied, assigned and compared in the normal way) and is default-constructible can be stored in a table.

Code

Check it out from git:

 git clone https://codeberg.org/andybalaam/nndb.git

Build it like this:

 sudo apt-get install libboost-all-dev libloki-dev scons

 cd nndb
 scons

Contact

Please contact the NNDB developers by creating an issue.