Unique indexed column in where clause and mysql execution after finding first row Suppose in a table there are 2 columns: login and password

login is indexed as unique index, password not indexed.


query: SELECT * FROM mytable WHERE login = 'Jhon'
query: SELECT * FROM mytable WHERE login = 'Jhon' AND password = '123'


After finding first row, will mysql stop or continue searching?

What will mysql do in first case 1. and 2. ?
If the constraint on login is unique... any serious sql database vendor will stop searching at the first and only possible occurence met. 

In the second case, it will stop at the first and only possible occurence, and returns the record if the password is '123', nothing if not.