undefined reference to `mysql_init'

I have the most recent package:
sudo apt install mariadb-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
mariadb-server is already the newest version (1:10.1.43-0ubuntu0.18.04.1).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

The following program:

#include <iostream>
#include <mysql.h>
int main(int argc, char *argv[])

{ MYSQL *conn; conn=mysql_init(NULL); mysql_close(conn); return 0; }

when compiled with

g++ -I/usr/include/mariadb -I/usr/include/mariadb/mysql -L/usr/lib/x86_64-linux-gnu/ -lmariadb -lz -ldl -lm -lpthread my.cpp

gives the error:

/tmp/cchC9TlH.o: In function `main':
my.cpp.text+0x15): undefined reference to `mysql_init'
my.cpp.text+0x25): undefined reference to `mysql_close'
collect2: error: ld returned 1 exit status