Python:sqlite OR语句 [英] Python: sqlite OR statement

问题描述

是否存在OR sqlite语句?我一直在尝试使用google，但是google似乎正在过滤 OR .

Is there an OR sqlite statement? I've been trying to google it, but google seems to be filtering out the OR.

例如，如果我想在此表中找到某人(人)

For example if I wanted to find someone in this table (people)

people:
+--fname--+--lname--+--has_squirrel--+
|Eric     |Schmidt  |0               |
+---------+---------+----------------+
|Elvis    |Presley  |1               |
+---------+---------+----------------+
|Richard  |Stallman |0               |
+---------+---------+----------------+

名字叫猫王或理查德，我的查询是什么?

with a first name of either Elvis or Richard, what would my query be?

我已经尝试过从诸如fname =('Elvis'或'Richard')的人那里选择 select *之类的东西，但是总是返回 Eric Sc​​hmidt (正好相反)我想要的行)！

I've tried things like select * from people where fname=('Elvis' or 'Richard'), but that always returns Eric Schmidt (the exact opposite rows of what I want)!

我还尝试从fname ='Elvis'或'Richard'的人中进行 select *，但是返回 all 表中的所有行！

I've also tried select * from people where fname='Elvis' or 'Richard' but that returns all the rows in the table!

我正在Ubuntu 10.10上使用Python 2.6 sqlite3模块.有人可以给我关于sqlite或statement的快速解释，还是告诉我它是否不存在?我尝试进行RTFM，却找不到任何东西(在sqlite网站上搜索 OR 会吐出一堆错误！).

I'm using the Python 2.6 sqlite3 module on Ubuntu 10.10. Can someone give me a quick explanation of the sqlite OR statment or tell me if it doesn't exist? I've tried to RTFM and I couldn't find anything (searching for OR on the sqlite website spits out a bunch of errors!).

谢谢！

推荐答案

这将是其中之一:

SELECT * FROM people WHERE fname IN ('Elvis', 'Richard');
SELECT * FROM people WHERE fname = 'Elvis' OR fname = 'Richard';

我很惊讶您的第一个查询仍然有效，而在您的第二个查询中，或'Richard'基本上意味着 or 1 = 1 ，对于每个用户而言，这始终是正确的表格中的行.

I'm surprised your first query even works, and in your second, or 'Richard' basically means or 1=1, which is always true, for every row in your table.

您的计算机不像您那样思考.即使 fname ='Elvis'或'Richard'对您来说似乎很明显，RDBMS也不知道您的意思，而是显示如果fname等于'Elvis'或... true".它将字符串评估为布尔值，并且我假设由于字符串不为空，因此将其评估为true.就像我之前说的，然后继续从表中选择每一行.

Your computer doesn't think like you do. Even if fname = 'Elvis' or 'Richard' seems obvious to you, the RDBMS doesn't know what you mean and reads "if fname is equal to 'Elvis' or... true". It evalutes the string to a boolean, and I assume since it's not empty, it's evaluated to true. And proceeds to select every row from your table, as I said earlier.

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