CREATE TABLE authorship (authid VARCHAR(255), paperid VARCHAR(255)); CREATE TABLE authors (lname VARCHAR(255), fname VARCHAR(255), authid VARCHAR(255)); CREATE TABLE papers (paperid VARCHAR(255))
What is the last name of the author that has published the most papers?
    
SQL: SELECT t1.lname FROM authors AS t1 JOIN authorship AS t2 ON t1.authid = t2.authid JOIN papers AS t3 ON t2.paperid = t3.paperid GROUP BY t1.fname, t1.lname ORDER BY COUNT(*) DESC LIMIT 1