PostgreSQL lets you write queries straight in C. It is not bad. Definitely easier than straight libpq: https://www.postgresql.org/docs/current/ecpg.html

Example C code (requires ECPG pre-compilation step):

EXEC SQL BEGIN DECLARE SECTION; int v1; VARCHAR v2; EXEC SQL END DECLARE SECTION;

...

EXEC SQL DECLARE foo CURSOR FOR SELECT a, b FROM test;

...

do { ... EXEC SQL FETCH NEXT FROM foo INTO :v1, :v2; ... } while (...);