SQLite3 - 跨表 SELECT 查询

Question

我想要返回的是性能表中的所有booking_id 与预订表中night = 1 的所有booking_ids 匹配的所有seat_ids - 是INNER JOIN 的最佳方式做吗？

还是更像"""SELECT seat_id FROM performance WHERE booking_id=(SELECT * FROM booking WHERE night = ?""", (night_number))

上面我得到sqlite3.OperationalError: incomplete input错误。

connection = sqlite3.connect('collyers_booking_system.db')
cursor = connection.cursor()

cursor.execute(booking_table)
cursor.execute(performance_table)

connection.commit()

booking_table = """CREATE TABLE IF NOT EXISTS
booking(
booking_id TEXT PRIMARY KEY,
customer_id INTEGER,
night INTEGER,
cost REAL,
FOREIGN KEY (customer_id) REFERENCES customer(customer_id)
)"""

performance_table = """CREATE TABLE IF NOT EXISTS
performance(
performance_id TEXT PRIMARY KEY,
seat_id TEXT,
booking_id INTEGER,
FOREIGN KEY (seat_id) REFERENCES seat(seat_id),
FOREIGN KEY (booking_id) REFERENCES booking(booking_id),
)"""

night_number = 1

cursor.execute("""SELECT seat_id FROM performance INNER JOIN booking ON night=?""", (night_number))
booked_seats = cursor.fetchall()

print(booked_seats)

这样我得到ValueError: parameters are of unsupported type 错误。

Answer 1

首先，如果这是您的实际代码，则表 performance 的 CREATE 语句中有错字。
您必须删除末尾的,：

FOREIGN KEY (booking_id) REFERENCES booking(booking_id), 

那么，这里：

cursor.execute("""SELECT seat_id FROM performance WHERE booking_id=(SELECT * FROM booking WHERE night = ?""", (night_number))

您错过了 sql 语句的右括号，子查询可能返回多于 1 行，因此您应该使用 = 而不是 IN。
此外，参数night_number 应作为元组传递，而不仅仅是数字，通过在括号内添加,：

cursor.execute("""SELECT seat_id FROM performance WHERE booking_id IN (SELECT * FROM booking WHERE night = ?)""", (night_number,))

对于连接，您需要一个适当的 ON 子句，它链接表和 , 以创建 night_number 的元组：

sql = """
SELECT p.seat_id 
FROM performance p INNER JOIN booking b 
ON b.booking_id = p. booking_id
WHERE b.night=?
"""
cursor.execute(sql, (night_number,))

两种方式，运算符IN 和连接都可以工作。
还有另一种有时表现更好的选择，这是EXISTS：

sql = """
SELECT p.seat_id 
FROM performance p 
WHERE EXISTS (
  SELECT 1 FROM booking b 
  WHERE b.night=? AND b.booking_id = p.booking_id
)
"""
cursor.execute(sql, (night_number,))

Answer 2

您正在将列表结果与整数进行比较。

this SELECT * FROM booking WHERE night = ? => 返回 N 行 而你正在等待一个整数SELECT seat_id FROM performance WHERE booking_id=?。

你必须使用这样的东西：

SELECT seat_id FROM performance WHERE booking_id in (SELECT * FROM booking WHERE night = ?""", (night_number))