Suppose you have a shell script that must write to a temporary file. How can you
ensure that this file doesn't exist and will not be overwritten by something
else?


The correct answer to this is to use the $$ variable to insert the pid into the
filename.



Assume you have a database table with a list of accounts and another table with
a list of transactions. How can I find how many accounts don't have a
transaction.


SELECT COUNT(account)
FROM Account OUTER JOIN AccountTrans
WHERE AccountTrans.Account = null;


Google get queries from around the world. Write a function that will return a
two character string representing a country code given an IP address as its
input.



You are at a party with a friend and 10 people are present including you and the
friend. Your friend makes you a wager that for every person you find that has
the same birthday as you, you get $1; for every person he finds that does not
have the same birthday as you, he gets $2. Would you accept the wager?"


"The answer has to do with the number of days in the year and the probability
the person’s birthday falls on the same day as mine (without replacement). I
eventually solved it, but it took time learning how to apply probability with no
replacement."