Related with count, max and group by - sql

Here is my table. I am trying to get distinct person distinct fruit based on maximum number of fruits he has.
persons | fruits
David apple
David apple
David apple
David banana
David orange
Sam apple
Sam banana
Sam orange
Sam orange
Sam orange
Sam orange
Tom apple
Tom banana
Tom banana
Tom orange
I want to see my result as:
persons | fruits
David apple
Sam orange
Tom banana
I tried using count and max functions and group by, but was not able to get right result.


You can use distinct on:
select distinct on (person) person, fruit
from (select person, fruit, count(*) as cnt
from personfruits pf
group by person, fruit
) pf
order by person, cnt desc;
You can write this without the subquery as well:
select distinct on (person) person, fruit
from personfruits pf
group by person, fruit
order by person, count(*) desc;
However, that is a bit hard to follow for someone not really familiar with distinct on.


From what I understand, you want to see which fruit occurs most often, per person. If that's correct, this should work
SELECT persons, fruits
FROM (
SELECT
persons,
fruits,
RANK() OVER(PARTITION BY persons ORDER BY FruitCount DESC) AS FruitRank -- Rank fruit count per person
FROM (
SELECT
persons,
fruits,
count(*) FruitCount -- get # rows per (person, fruit) combination
FROM MyTable
GROUP BY persons, fruits
) src
) src
WHERE FruitRank = 1 -- Return fruit with largest FruitCount, per person

Related

How Do I Filter My Results Based Off Of Other Entries?

I have written a statement that retrieves the person name, as well as the food they've eaten.
Person | Food Eaten
John | Cake
Jack | Ice Cream
Louis | Hot Dog
John | Pineapple Pizza
Now that I've retrieved what foods people have eaten, I would like to remove anyone who has eaten Pineapple Pizza from my list.
What type of clause would I want to use to create a unique list of people who haven't eaten Pineapple Pizza?

You can use not exists :
select t.*
from table t
where not exists (select 1
from table t1
where t1.person = t.person and t1.food = 'Pineapple Pizza'
);

If you know the exact value of the food people have eaten, you can exclude it when you write your WHERE clause.
SELECT t.person, t.food_eaten
FROM eaten_tbl t
WHERE t.food_eaten <> 'Pineapple Pizza';

hive sql adding record count as column

I have records similar to the below
fruit day
apple 1/1/1990
apple 1/2/1990
apple 1/3/1990
plum 1/1/1990
orange 1/1/1990
orange 1/2/1990
orange 1/3/1990
I want to keep a running total for items for each day assuming item will increase by 1 every day. For example
fruit day count
apple 1/1/1990 1
apple 1/2/1990 2
apple 1/3/1990 3
plum 1/1/1990 1
orange 1/1/1990 1
orange 1/2/1990 2

You could use windowed COUNT:
SELECT *, COUNT(*) OVER(PARTITION BY fruit ORDER BY day)
FROM tab;
DBFiddle Demo

You can also use subquery:
select *,
(select count(*) from table where fruit = t.fruit and day <= t.day) count
from table t;

Using a query to return the most frequent value and the count within a group using SQL in MS Access

Say I have a table showing the type of fruit consumed by an individual over a 24 hour period that looks like this:
Name Fruit
Tim Apple
Tim Orange
Tim Orange
Tim Orange
Lisa Peach
Lisa Apple
Lisa Peach
Eric Plum
Eric Orange
Eric Plum
How would I get a table that shows only the most consumed fruit for each person, as well as the number of fruits consumed. In other words, a table that looks like this:
Name Fruit Number
Tim Orange 3
Lisa Peach 2
Eric Plum 2
I tried
SELECT Name, Fruit, Count(Fruit)
FROM table
GROUP BY Name
But that returns an error because Name needs to be in the GROUP BY statement as well. Every other method I've tried returns the counts for ALL values rather than just the maximum values. MAX(COUNT()) doesn't appear to be a valid statement, so I'm not sure what else to do.

This is a pain, but you can do it. Start with your query and then use join:
SELECT n.Name, n.Fruit
FROM (SELECT Name, Fruit, Count(Fruit) as cnt
FROM table as t
GROUP BY Name, Fruit
) as t INNER JOIN
(SELECT Name, max(cnt) as maxcnt
FROM (SELECT Name, Fruit, Count(Fruit) as cnt
FROM table
GROUP BY Name, Fruit
) as t
GROUP BY Name
) as n
ON t.name = n.name and t.cnt = n.maxcnt;

Oracle find common value in two different columns

If I have a structure like this:
CREATE TABLE things (
id,
personA varchar2,
personB varchar2,
attribute ...,
)
And I want to find, for a given attribute, if I have at least 1 common person for all my things, how would I go about it?
So if my data is (and it could be more than 2 per attribute):
1, John, Steve, Apple
2, Steve, Larry, Apple
3, Paul, Larry, Orange
4, Paul, Larry, Orange
5, Chris, Michael, Tomato
6, Steve, Larry, Tomato
For Apple, Steve is my common person, For Orange both Paul and Larry are, and for Tomato I have no common people. I don't need a query that returns all of these at once, however. I have one of these attributes and want 0, 1, or 2 rows depending on what kind of commonality I have. I've been trying to come up with something but can't quite figure out.

This will give you your common person / attribute list. I ran it against your sample data and got the expected result. Hope it's at least pointing in the right direction :)
WITH NormNames AS (
SELECT PersonA AS Person, Attribute FROM things
UNION ALL SELECT PersonB AS Person, Attribute FROM things
)
SELECT
Person, Attribute, COUNT(*)
FROM NormNames
GROUP BY Person, Attribute
HAVING COUNT(*) >= 2

If you're on 11gR2 you could also use the unpivot operator to avoid the self-join:
select person, attribute
from (
select *
from things
unpivot (person for which_person in (persona as 'A', personb as 'B'))
)
group by person, attribute
having count(*) > 1;
PERSON ATTRIBUTE
---------- ----------
Steve Apple
Paul Orange
Larry Orange
3 rows selected.
Or to just the the people who match the attribute, which I think is what the end of your question is looking for:
select person
from (
select *
from things
unpivot (person for which_person in (persona as 'A', personb as 'B'))
)
where attribute = 'Apple'
group by person, attribute
having count(*) > 1;
PERSON
----------
Steve
1 row selected.
The unpivot translates columns into rows. Run on its own it transforms your original six rows into twelve, replacing the original persona/personb columns with a single person and an additional column indicating which column the new row was formed from, which we don't really care about here:
select *
from things
unpivot (person for which_person in (persona as 'A', personb as 'B'));
ID ATTRIBUTE W PERSON
---------- ---------- - ----------
1 Apple A John
1 Apple B Steve
2 Apple A Steve
2 Apple B Larry
3 Orange A Paul
3 Orange B Larry
4 Orange A Paul
4 Orange B Larry
5 Tomato A Chris
5 Tomato B Michael
6 Tomato A Steve
6 Tomato B Larry
12 rows selected.
The outer query is then doing a simple group.

Here's one method.
It implements an unpivot method by cross-joining to a list of numbers (you could use the unpivot method Alex uses) and then joins the result set, hopefully with a hash join for added goodness.
with
row_generator as (
select 1 counter from dual union all
select 2 counter from dual),
data_generator as (
select
attribute,
id ,
case counter
when 1 then persona
when 2 then personb
end person
from
things,
row_generator)
select
t1.attribute,
t1.person
from
row_generator t1,
row_generator t2
where
t1.attribute = t2.attribute and
t1.person = t2.person and
t1.id != t2.id;

How to produce detail, not summary, report sorted by count(*)?

Oracle 11g:
I want results to list by highest count, then ch_id. When I use group by to get the count then I loose the granularity of the detail. Is there an analytic function I could use?
SALES
ch_id desc customer
=========================
ANAR Anari BOB
SWIS Swiss JOE
SWIS Swiss AMY
BRUN Brunost SAM
BRUN Brunost ANN
BRUN Brunost ROB
Desired Results
count ch_id customer
===========================================
3 BRUN ANN
3 BRUN ROB
3 BRUN SAM
2 SWIS AMY
2 SWIS JOE
1 ANAR BOB

Use the analytic count(*):
select * from
(
select count(*) over (partition by ch_id) cnt,
ch_id, customer
from sales
)
order by cnt desc

select total, ch_id, customer
from sales s
inner join (select count(*) total, ch_id from sales group by ch_id) b
on b.ch_id = s.chi_id
order by total, ch_id
ok - the other post that happened at the same time, using partition, is the better solution for Oracle. But this one works regardless of DB.