确定sql语句是否以SELECT单词开头

Question

我正在尝试对输入的SQL字符串进行一些基本验证。我想确保查询的第一个单词是否则将SELECT引发错误。这里有些例子：

1) yes
SELECT * FROM table

2) no
# SELECT * FROM table;
DROP TABLE table;

3) no
   /* SELECT * FROM 
   TABLE */ DROP TABLE table;

4) yes
# here is a comment
SELECT * FROM table

5) yes
/* here is a
comment */ SELECT * FROM table

和其他各种。也许这更多是一个正则表达式解决方案或string.replace。但是，查看是否已输入SQL SELECT语句的一种好方法是什么？

Answer 1

我将为作业使用适当的工具sqlparse-SQL解析器，获取第一个语句对象，并检查其SELECT类型是否正确：

In [1]: import sqlparse

In [2]: queries = [
   ...:     "SELECT * FROM table",
   ...:     """
   ...:     # SELECT * FROM table;
   ...:     DROP TABLE table;
   ...:     """,
   ...:     """/* SELECT * FROM 
   ...:    TABLE /* DROP table table;""",
   ...:    """
   ...:    # here is a comment
   ...:    SELECT * FROM table
   ...:    """
   ...: ]

In [3]: def is_select(query):
             first_statement = next((token for token in sqlparse.parse(query) if isinstance(token, sqlparse.sql.Statement)), None) 
             if first_statement:
                 return first_statement.get_type() == 'SELECT'

In [4]: for query in queries:
    ...:     print(query, is_select(query))

    SELECT * FROM table 
    True

    # SELECT * FROM table;
    DROP TABLE table;
    False

   /* SELECT * FROM 
   TABLE /* DROP table table; 
   False

   # here is a comment
   SELECT * FROM table
   True