% 让 Python 原始 SQL 查询困惑

Question

根据这个StackOverflow的问题，我想用以下的原始SQL命令在Python中“清空”与某个Django应用相关的所有表：

cursor.execute("set foreign_key_checks = 0")
cursor.execute("select concat('truncate table ',table_schema,'.',table_name,';') as sql_stmt from information_schema.tables where table_schema = 'my_db' and table_type = 'base table' AND table_name LIKE 'some_prefix%'")
for sql in [sql[0] for sql in cursor.fetchall()]:
    cursor.execute(sql)
cursor.execute("set foreign_key_checks = 1")

可惜我遇到了以下错误：

C:\dev\my_project>my_script.py
Traceback (most recent call last):
  File "C:\dev\my_project\my_script.py", line 295, in <module>
    cursor.execute(r"select concat('truncate table ',table_schema,'.',table_name,';') as sql_stmt from information_schema.tables where table_schema = 'my_db' and table_type = 'base table' AND table_name LIKE 'some_prefix%'")
  File "C:\Python26\lib\site-packages\django\db\backends\util.py", line 18, in execute
    sql = self.db.ops.last_executed_query(self.cursor, sql, params)
  File "C:\Python26\lib\site-packages\django\db\backends\__init__.py", line 216, in last_executed_query
    return smart_unicode(sql) % u_params
TypeError: not enough arguments for format string

在LIKE中使用的%是不是造成了问题？我该怎么解决这个问题呢？

Answer 1

你试过 %% 吗？这个在 Python 的字符串格式化中可以用来表示一个 % 符号。