MySQL Counting Distinct Values on Multiple Columns

Question

I wrote a script that runs each time a user logs into a computer in our domain. This script makes a record of the user as well as the computer they logged into. Any number of users can log into any number of computers.

I just inherited this IT environment from a consultant who is no longer around, and I'm writing this little query so when I get a call from a user, I can search by that user's name and reasonably predict which computer they are using by the number of times they've logged into any given computer.

Here's a sample of the data in the 'login' table:

    COMPUTER        USER
    ncofp02         lee
    ncofp02         lee
    ncofp02         andy
    ncodc01         andy
    ncodc01         andy
    ncodc01         lee

What I'm banging my head on is the logic to count distinct values across multiple columns. I'd like to see a result like this:

    COMPUTER       USER   COUNT
    ncofp02        lee    (2)
    ncofp02        andy   (1)
    ncodc01        lee    (1)
    ncodc01        andy   (2)

Is there a way to accomplish this with a single query within mysql, or should I start looping some php? (booooo!)

Solution 1

Just list multiple columns in the GROUP BY clause.

SELECT computer, user, count(*) AS count
FROM login
GROUP BY computer, user

Solution 2

Try this:

SELECT l.computer, l.user, COUNT(DISTINCT l.computer, l.user) AS count
FROM login l 
GROUP BY l.computer, l.user

Solution 3

Easy!

SELECT 
    computer, user, COUNT(DISTINCT computer, user) AS count
FROM 
    login 

Comments

[Admin]

Thank you! I can't believe it was seriously THAT easy. LOL I guess I must have been overthinking. Thanks again!

[Barmar]

You don't need DISTINCT if you're counting the same thing you're grouping by.