A select query does not performs case-sensitive query which means if the user name is pravesh, Pravesh, PRAVESH then it will select all users using simple select. Below example of normal mysql select query -
SELECT * FROM tablename WHERE username=pravesh
But if you want a query to be case sensitive then you can use BINARY keyword in query-
SELECT * FROM tablename WHERE BINARY username =pravesh
this will select only those user that exactly matches with user name pravesh and not Pravesh and PRAVESH.
In this case "BINARY" keyword is helpful for you to differentiate with cases.