A fast and futuristic database for your projects.

We have already written an initial article aboutDuckDB that explains initial concepts, installation and first steps. For more information, access the link:

• Meet DuckDB, a modern database

In this article, we will see how to connect to DuckDB using the API withC++

01. Download the lib and create a basic code

TheDuckDB API for C++ is not yet stable, on the API page itself there is this warning:

DuckDB's C++ API is internal. It is not guaranteed to be stable and can change without notice. If you would like to build an application on DuckDB, we recommend using the C API.

That's why they recommend that you use theCAPI which works perfectly. To do this, just access the page:https://duckdb.org/docs/installation/ and choose the data according to your system. In my case, I chose:

• Stable Release:C/C++:Linux:Direct download:x86_64

Then just click on the.zip that will be made available and download it, or download it withwget:

wget-q https://github.com/duckdb/duckdb/releases/download/v1.3.1/libduckdb-linux-amd64.zip

Unzip:

unzip libduckdb-linux-amd64.zip-d libduckdb-linux-amd64

Create a database and table, example:duckdb terminalroot.db

CREATETABLEterminalroot(idINTEGER,nameSTRING);INSERTINTOterminalrootVALUES(1,'Marcos Oliveira');INSERTINTOterminalrootVALUES(2,'Mark Raasveldt');INSERTINTOterminalrootVALUES(3,'Hannes Muhleisen');SELECT*FROMterminalroot;.exit

Go into the directory you unzipped and create some basic code:cd libduckdb-linux-amd64/ && vim main.cpp

#include"duckdb.h"#include<iostream>intmain(){duckdb_databasedb;duckdb_connectioncon;duckdb_resultresult;if(duckdb_open("terminalroot.db",&db)==DuckDBError){std::cerr<<"Error opening database\n";return1;}if(duckdb_connect(db,&con)==DuckDBError){std::cerr<<"Error connecting to database\n";return1;}if(duckdb_query(con,"SELECT * FROM terminalroot;",&result)==DuckDBError){std::cerr<<"Error executing SELECT\n";duckdb_disconnect(&con);duckdb_close(&db);return1;}for(idx_trow=0;row<=result.deprecated_column_count;row++){intid=duckdb_value_int32(&result,0,row);constchar*name=duckdb_value_varchar(&result,1,row);std::cout<<id<<" | "<<name<<'\n';duckdb_free((void*)name);// free varchar memory}duckdb_destroy_result(&result);duckdb_disconnect(&con);duckdb_close(&db);}

Compile and run:

g++ main.cpp libduckdb.soLD_LIBRARY_PATH=. ./a.out

Probable output:

1 | Marcos Oliveira2 | Mark Raasveldt3 | Hannes Muhleisen

Install on the system

If you want to install on your system and compile with the-lduckdb flag, run the commands below:

• 01. Move.h toinclude:

sudo mkdir-p /usr/local/include/duckdbsudo cpduckdb.h /usr/local/include/duckdb/

• 02. Move thedynamic library tolib> And update the system's shared library cache.

sudo cplibduckdb.so /usr/local/lib/sudoldconfig

After that, just test with the flag and you don't even need to be in the folder with the downloaded files or use theLD_LIBRARY_PATH environment variable:

But you needterminalroot.db, if you put the absolute path, e.g.:"/home/$USER/.db/terminalroot.db" your binary will run regardless of where you are in the system!

g++ main.cpp-lduckdb./a.out

If you want to create.pc forpkg-config, expand the procedure below:

Create the file/usr/local/lib/pkgconfig/duckdb.pc with this content:

prefix=/usr/localexec_prefix=${prefix}libdir=${exec_prefix}/libincludedir=${prefix}/includeName: DuckDBDescription: DuckDB embedded databaseVersion: 1.2.1Libs: -L${libdir} -lduckdbCflags: -I${includedir}/duckdb

Save with:

sudo mkdir-p /usr/local/lib/pkgconfigsudovim /usr/local/lib/pkgconfig/duckdb.pc# paste the above content

Refresh the cache:

exportPKG_CONFIG_PATH=/usr/local/lib/pkgconfig:$PKG_CONFIG_PATH

I tried the static librarylibduckdb_static.a, but had problems, but if you prefer, try:

g++ main.cpp libduckdb_static.a-I.-ldl-pthread-lm-lz-static-libstdc++-static-libgcc

If you also have problems, check for missing dependencies:

nm libduckdb_static.a |grep" U "

("U" =undefined symbol)

Or useldd ./a.out to see if there are still dynamic libs hanging.

In my case none of these steps worked, but see if they apply to you too.

Useful links

• For.hpp:https://stackoverflow.com/questions/71782764/how-to-add-duckdb-library-in-c-program
• https://duckdb.org/docs/stable/clients/cpp
• https://duckdb.org/docs/stable/clients/c/connect