MySQL 检查登录详细信息（用户名和密码）的最佳查询
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Optimal query for checking login details(username and password)
提问by Sajith
Which is optimal query for check whether the username ans password present in MySql database.
这是检查 MySql 数据库中是否存在用户名和密码的最佳查询。
1)SELECT * FROM login_details WHERE username='username' AND password='password'
2)SELECT count(*)FROM login_details WHERE username='username' AND password='password'
3)SELECT count(Username)FROM login_details WHERE username='username' AND password='password'
4)SELECT 1 FROM login_details WHERE username='username' AND password='password'
Thanks
谢谢
回答by eggyal
Hopefully 'password'is actually a salted hash of the user's password, and you're passing both literals from your application as parameters to a prepared statement.
希望'password'实际上是用户密码的加盐散列，并且您将应用程序中的两个文字作为参数传递给准备好的语句。
Assuming that you have an index on (username, password), the "optimum" would be:
假设您在 上有一个索引(username, password)，“最佳”将是：
SELECT EXISTS (
SELECT * FROM login_details WHERE username = ? AND password = ?
)
This way, MySQL stops searchingonce it encounters a single result.
这样，一旦遇到单个结果，MySQL 就会停止搜索。
