为什么我们可以使用string.Format来组成sql语句，但还是执行SQLiteCommand，Parameters.add?

问题描述

我在许多教程中看到了使用变量和参数来组成sql语句的内容.

I saw in many tutorial that compose sql statement by using variable and Parameters.Add likt this

public void updateStudent(String @studentID, String @firstName, String @lastName)
{
    SQLiteCommand command = conn.CreateCommand();
    command.CommandText = "UPDATE Students SET firstName = @firstName, lastName = @lastName WHERE studentID = @studentID";
    command.Parameters.Add(new SQLiteParameter("@studentID", @studentID));
    command.Parameters.Add(new SQLiteParameter("@firstName", @firstName));
    command.Parameters.Add(new SQLiteParameter("@lastName" , @lastName));
    command.ExecuteNonQuery();
}

我们为什么不使用

string.Format("Update Students SET firstName = '{0}', lastName = '{1}...", @firstName, @lastname)

有什么好处吗?

推荐答案

四个原因:

• 避免 SQL注入攻击
• 避免包含真正撇号的字符串出现问题，而无意引起SQL注入攻击(例如，姓氏"O'Reilly"
)
• 避免字符串不必要的转换，这可能由于文化原因而导致失败(例如，"1.23"和"1,23"之间的差异取决于您的文化
• 分开保存代码(SQL)和数据(参数)以提高可读性

• Avoiding SQL injection attacks
• Avoiding problems with strings containing genuine apostrophes with no intention of causing a SQL injection attack (e.g. a last name of "O'Reilly"
• Avoiding string unnecessary conversions, which can cause failures for cultural reasons (e.g. the difference between "1.23" and "1,23" depending on your culture
• Keeping the code (SQL) and the data (parameters) separate for cleaner readability

还请注意:

• 这不是特定于SQLite的.这是所有数据库的最佳做法.

• 除非变量是关键字，否则不需要使用 @ 作为变量的前缀.所以写起来会更惯用:

• This isn't SQLite specific. It's best practice for all databases.

• You don't need to use @ as a prefix to your variables unless they're keywords. So it would be more idiomatic to write:

command.Parameters.Add(new SQLiteParameter("@lastName", lastName));

(同上，方法参数声明以...开头，但不是在SQL语句中.)

(Ditto for the method parameter declarations to start with... but not the parametersinside the SQL statement.)

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