问题描述
我想用MySQL执行SELECT查询.我的目标是在兽医数据库中选择所有狗，它们分别是sex=male和fur=short和(color=black or size=big)
I would like to perform a SELECT query with MySQL. My goal is to select all the dogs in a vet database that would be sex=male and fur=short and (color=black or size=big)
注意:我要选择黑色或大狗.他们不必满足2个要求.他们只需要实现其中一个即可.
Note: I want to select dogs that are either black or size is big. They don't have to fulfill the 2 requirements. They just need to fulfill either one.
我已经在下面编写了SQL语句，但是我不确定我是否正确:
I have written the SQL statement below but I'm not not sure if I'm right:
SELECT name, sex, fur, color
FROM dogs
WHERE TRUE sex='male' AND fur='short' AND color='black' OR size="big";
如果太混乱，请原谅我的措辞.
Pardon my phrasing if it's too confusing.
推荐答案
根据 MySQL的运算符优先级 AND的优先级高于OR.
所以C1 AND C2 OR C3将被视为(C1 AND C2) OR C3
要覆盖默认优先级，您需要使用括号:C1 AND (C2 OR C3)
To override the default precedence you need to use parenthesis as:C1 AND (C2 OR C3)
对于您而言，正确的查询是:
In your case the right query is:
SELECT name, sex, fur, color
FROM dogs
WHERE sex='male' AND fur='short' AND (color='black' OR size="big");
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