如何在Python中使用SQL语句中的变量？

Question

如何在Python中使用SQL语句中的变量？好吧，我对Python没什么经验。我有以下Python代码：cursor.execute("INSERT INTO table VALUES var1, var2, var3,")哪里var1是整数，var2 & var3是弦乐。如果没有python作为查询文本的一部分，我如何编写变量名？

Answer 1

很多方法。别使用最明显的(%s带着%)在实际代码中，它对攻击.

# Never do this -- insecure!

symbol = 'RHAT'

c.execute("SELECT * FROM stocks WHERE symbol = '%s'" % symbol)

# Do this instead

t = ('RHAT',)

c.execute('SELECT * FROM stocks WHERE symbol=?', t)

print c.fetchone()

# Larger example that inserts many records at a time

purchases = [('2006-03-28', 'BUY', 'IBM', 1000, 45.00),

             ('2006-04-05', 'BUY', 'MSFT', 1000, 72.00),

             ('2006-04-06', 'SELL', 'IBM', 500, 53.00),

            ]

c.executemany('INSERT INTO stocks VALUES (?,?,?,?,?)', purchases)

如果您需要更多的示例：

# Multiple values single statement/execution

c.execute('SELECT * FROM stocks WHERE symbol=? OR symbol=?', ('RHAT', 'MSO'))

print c.fetchall()

c.execute('SELECT * FROM stocks WHERE symbol IN (?, ?)', ('RHAT', 'MSO'))

print c.fetchall()

# This also works, though ones above are better as a habit as it's inline with syntax of executemany().. but your choice.

c.execute('SELECT * FROM stocks WHERE symbol=? OR symbol=?', 'RHAT', 'MSO')

print c.fetchall()

# Insert a single item

c.execute('INSERT INTO stocks VALUES (?,?,?,?,?)', ('2006-03-28', 'BUY', 'IBM', 1000, 45.00))

Answer 2

cursor.execute("INSERT INTO table VALUES (%s, %s, %s)", (var1, var2, var3))

注意，参数作为元组传递。

数据库API对变量进行适当的转义和引用。小心不要使用字符串格式运算符(%)，因为

1. 它不做任何逃避或引用。
   
2. 它容易受到不受控制的字符串格式攻击。