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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!)
829
but when we want to count distinct column combinations, we must either clumsily concatenate values (and be very careful to choose the right separator): select count(distinct col1 || '-' || col2) from mytable; or use a subquery: select count(*) from (select distinct col1, col2 from mytable);
We can use the DISTINCT clause on more than columns in MySQL. In this case, the uniqueness of rows in the result set would depend on the combination of all columns.
Answer. Yes, the DISTINCT clause can be applied to any valid SELECT query. It is important to note that DISTINCT will filter out all rows that are not unique in terms of all selected columns.
Yes, DISTINCT works on all combinations of column values for all columns in the SELECT clause.
Just list multiple columns in the GROUP BY clause.
SELECT computer, user, count(*) AS count FROM login GROUP BY computer, user If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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