SQL Nested Query with distinct count - sql

Question

I have a dilemma, and I'm hoping someone will be able to help me out. I am attempting to work on some made up problems from an old text book of mine, this isn't a question from the book, but the data is, I just wanted to see if I could still work in SQL, so here goes. When this code is executed,
SELECT COUNT(code_description) "Number of Different Crimes", last, first,
code_description
FROM
(
SELECT criminal_id, last, first, crime_code, code_description
FROM criminals
JOIN crimes USING (criminal_id)
JOIN crime_charges USING (crime_id)
JOIN crime_codes USING (crime_code)
ORDER BY criminal_id
)
WHERE criminal_id = 1020
GROUP BY last, first, code_description;
I am provided with these results:
Number of Different Crimes LAST FIRST CODE_DESCRIPTION
1 Phelps Sam Agg Assault
1 Phelps Sam Drug Offense
Inevitably, I would like the number of different crimes to be 2 for each line since this criminal has two unique crimes charged to him. I would like it to be displayed something like:
Number of Different Crimes LAST FIRST CODE_DESCRIPTION
2 Phelps Sam Agg Assault
2 Phelps Sam Drug Offense
Not to push my luck but I would also like to get rid of the follow line also:
WHERE criminal_id = 1020
to something a little more elegant to represent any criminal with more than 1 crime type associated with them, for this case, Sam Phelps is the only one in this data set.

Answer 1

As #sgeddes said in a comment, you can use an analytic count, which doesn't need a subquery if you're specifying the criminal ID:
SELECT COUNT(code_description) OVER (PARTITION BY first, last) AS "Number of Different Crimes",
last, first, code_description
FROM criminals
JOIN crimes USING (criminal_id)
JOIN crime_charges USING (crime_id)
JOIN crime_codes USING (crime_code)
WHERE criminal_id = 1020;
If you want to look for anyone with multiple crimes then you do need a subquery so you can filter on the analytic result:
SELECT charge_count AS "Number of Different Crimes",
last, first, code_description
FROM (
SELECT COUNT(DISTINCT code_description) OVER (PARTITION BY first, last) AS charge_count,
criminal_id, last, first, code_description
FROM criminals
JOIN crimes USING (criminal_id)
JOIN crime_charges USING (crime_id)
JOIN crime_codes USING (crime_code)
)
WHERE charge_count > 1
ORDER BY criminal_id, code_description;
SQL Fiddle demo.
If the charges are across multiple crimes, but duplicated, then the distinct count still works, but you might want to make add a distinct to the overall result set - unless you want to show other crime-specific info - otherwise you get something like this.