for one, duckdb includes all of sqlite (and many other dependencies). it knows how to do things like efficiently query over parquet files in s3. it's expansive - a swiss army knife for working with data wherever it's at.

sqlite is a "self contained system" depending on no external software except c standard library for target os:

> A minimal build of SQLite requires just these routines from the standard C library:

> memcmp(), memcpy(), memmove(), memset(), strcmp(), strlen(), strncmp()

> Most builds also use the system memory allocation routines:

> malloc(), realloc(), free()

> Default builds of SQLite contain appropriate VFS objects for talking to the underlying operating system, and those VFS objects will contain operating system calls such as open(), read(), write(), fsync(), and so forth

Quoting from the appropriately named https://sqlite.org/selfcontained.html

as a very rough and unfair estimate between the two project's source, sqlite is about 8% the size of duckdb:

    $ pwd
    /Users/jitl/src/duckdb/src
    $ sloc .
    
    ---------- Result ------------
    
                Physical :  418092
                  Source :  317274
                 Comment :  50113
     Single-line comment :  46187
           Block comment :  3926
                   Mixed :  4415
     Empty block comment :  588
                   Empty :  55708
                   To Do :  136
    
    Number of files read :  2611
    
    ----------------------------
    $ cd ~/Downloads/sqlite-amalgamation-3500400/
    $ sloc .
    
    ---------- Result ------------
    
                Physical :  34742
                  Source :  25801
                 Comment :  8110
     Single-line comment :  1
           Block comment :  8109
                   Mixed :  1257
     Empty block comment :  1
                   Empty :  2089
                   To Do :  5
    
    Number of files read :  2
    
    ----------------------------