在 CS50 中学习 SQL：运行时错误：接近 "IF"：语法错误

Question

我正在尝试创建一个名为 stock 的表，用于跟踪某人在购买一定数量后拥有多少股票。这是我迄今为止尝试过的最复杂的SQL代码，我认为我写错了东西。有人可以发现错误吗？

db.execute("IF EXISTS (SELECT * FROM stock WHERE symbol = :symbol AND userid = :userid) 
UPDATE stock SET (amount = amount + 1) WHERE userid = :userid 
ELSE INSERT INTO stock (userid, symbol, amount) 
VALUES ((SELECT id FROM users WHERE id = :userid), 
:symbol, :amount", userid = session["user_id"], symbol = symbol, amount = share_number)

Answer 1

您缺少括号

INSERT INTO stock (userid, symbol, amount) 
VALUES ((SELECT id FROM users WHERE id = :userid), :symbol, :amount

而不是(SELECT id FROM users WHERE id = :userid)你可以简单地写

INSERT INTO stock (userid, symbol, amount) 
VALUES (:userid, :symbol, :amount)