P5R7hMVR

1CREATE TABLE IF NOT EXISTS statistics (
2    user_id     BIGINT,
3    purchase_id INTEGER,
4    site_id     INTEGER,
5    FOREIGN KEY (user_id) REFERENCES users(user_id)
6                                      on DELETE NO ACTION ,
7    FOREIGN KEY (purchase_id) REFERENCES purchases(purchase_id)
8                                      on DELETE NO ACTION ,
9    FOREIGN KEY (site_id) REFERENCES sites(site_id)
10                                      on DELETE NO ACTION,
11    PRIMARY KEY (user_id)
12);
13
14#  2.вопроса немного не понял