CREATE TABLE review (a_id NUMBER, u_id NUMBER, i_id NUMBER, rating NUMBER, rank NUMBER)
CREATE TABLE item (i_id NUMBER, title VARCHAR2)
CREATE TABLE useracct (u_id NUMBER, name VARCHAR2)
CREATE TABLE trust (source_u_id NUMBER, target_u_id NUMBER, trust NUMBER)

For each user, return the name and the average rating of reviews given by them. Plot them as pie chart.
SELECT name, AVG(T2.rating) FROM useracct AS T1 JOIN review AS T2 ON T1.u_id = T2.u_id GROUP BY T2.u_id
SELECT "name", AVG("T2"."rating") FROM "useracct" "T1" JOIN "review" "T2" ON "T1"."u_id" = "T2"."u_id" GROUP BY "T2"."u_id"