Slide 98
Slide 98 text
N+1 Query
SELECT user_id FROM comments;
SELECT * FROM user WHERE id = 1;
SELECT * FROM user WHERE id = 2;
SELECT * FROM user WHERE id = 3;
SELECT * FROM user WHERE id = 4;
SELECT * FROM user WHERE id = 5;
SELECT * FROM user WHERE id = 6;
…
# JOIN 1 query
SELECT * FROM comments, users WHERE comments.user_id = users.id;
# 2 query
SELECT user_id FROM comments;
SELECT * FROM users WHERE users.id IN [1, 2, 3, 4, 5, 6];