I have persons i one table [person] and cars [car] registered to each person i another, connected by id.
I want to get a list of how many persons having how many cars.
Something like this:
PERSON
id
name
1
LISA
2
ADAM
3
RAY
CARS
id
id_person
brand
1
3
FORD
2
1
BMW
3
2
VOLVO
4
1
VOLVO
5
1
VW
RESULT
no cars
no persons
1
2
2
0
3
1
Just dont get how to do it?
You need to do it in two stages. The first is to get the number of cars per person -
SELECT p.id, COUNT(*) num_cars
FROM person p
JOIN cars c ON p.id = c.id_person
GROUP BY p.id
This can then be nested to count people per count -
SELECT num_cars, COUNT(*) num_people
FROM (
SELECT p.id, COUNT(*) num_cars
FROM person p
JOIN cars c ON p.id = c.id_person
GROUP BY p.id
) t
GROUP BY num_cars
ORDER BY num_cars ASC
Related
I have four tables detailing an amusement park and its guests' ride history.
Categories
c_id name
1 Thrill
2 Leisure
3 Kiddie
Rides
r_id c_id
1 1
2 1
3 2
4 2
5 3
6 3
guest_history
h_id g_id
1 1
2 1
3 2
4 3
history_items
h_id r_id
1 5
2 6
3 1
3 2
4 5
How would I get all of the guests (g_id's) that have either rode all of the kiddie rides or none of the kiddie rides?
Expected Output would be:
g_id
1
2
I can't seem to figure out what the easiest way to go about it would be. I can only seem to conjure up a table that contains all of the cases that a guest has rode a kiddie ride. My attempt was a 4-way inner join of the tables and to filter out on the c_id = "Kiddie". Any help would be appreciated.
You can try this below logic-
3 is fixed in the query to get category "Kiddie"
DEMO HERE
SELECT A.g_id,COUNT(C.r_id)
FROM guest_history A
INNER JOIN history_items B ON A.h_id = B.h_id
INNER JOIN Rides C ON B.r_id = C.r_id AND C.c_id = 3
GROUP BY A.g_id
HAVING COUNT(DISTINCT B.r_id) = (SELECT COUNT(r_id) FROM Rides WHERE c_id = 3)
OR COUNT(DISTINCT B.r_id) = 0
SELECT g_id
FROM Categories
NATURAL JOIN Rides
NATURAL JOIN guest_history
NATURAL JOIN history_items
GROUP BY g_id
HAVING COUNT(DISTINCT r_id) IN (0,
(SELECT COUNT(DISTINCT r_id)
FROM Categories
NATURAL JOIN Rides
WHERE name = 'Kiddie')
)
fiddle
I have the following tables:
Table users
id name base_discount
1 jack 10
2 michael 20
3 richard 30
Table item
id name category_id price
1 hammer 1 10
2 knife 2 15
3 spoon 2 12
4 plate 3 20
5 tree 4 400
Table category
id name
1 tools
2 kitchen
3 dishes
4 garden
Table discount_category
id user_id category_id discount
1 1 1 20
2 1 3 25
3 3 3 10
4 1 2 15
Table discount_item
id user_id item_id discount
1 2 1 50
2 1 2 50
Now what I want to achieve. I want to attach the discount per item that a user has to the correct item. If that is not available (NULL) I want to attach the discount per category that a user has. And if that is not available (NULL), I want to attach the base discount that a user has. With the discount I then calculate the new price of the item. However, when I try using COALESCE() within SUM() I get a syntax error. What am I doing wrong?
Below is my current query:
SELECT item.id, item.name, category.id,
category.name AS category_name, item.price, SUM((100 -
COALESCE(
(
SELECT discount_item.discount
FROM discount_item
INNER JOIN users ON discount_item.user_id = users.id
WHERE users.id = '1' AND discount_item.item_id = item.id
),
(
SELECT discount_category.discount
FROM discount_category
INNER JOIN users ON discount_category.user_id = users.id
WHERE users.id = '1' AND discount_category.category_id = item.category_id
),
(
SELECT users.base_discount
FROM users
WHERE users.id = '1'
)
)) / 100 * item.price) AS new_price,
FROM item
INNER JOIN category ON item.category_id = category.id;
Please also see the below link for an SQL Fiddle (couldn't do it on sqlfiddle.com as it wouldn't load). In the example I have appended a suffix to each table name.
http://rextester.com/LCCKSD59098
You have an extra comma after new_price and before FROM ITEM, hence the error.
Rextester Demo
Do not select other columns in select if you are not using them in group by, as in other relational RDBMS, you will get error.
Also use alias for table names for better readibily and to avoid confusion.
I have to count products inside each category like I have a category A that have two childs B and C.
In B category have 10 products and C category have 5 Products.
I want to write a query that count product like A = 15 B = 10 C = 5.
I have wrote a query that count only for child categories.
My query is given below
SELECT
c.`id`,
c.`parent_id`,
c.`name`,
c.`slug`,
c.`route_id`,
c.`description`,
c.`excerpt`,
c.`sequence`,
c.`image`,
c.`seo_title`,
c.`meta`,
c.`enabled`,
(SELECT
COUNT(`product_id`)
FROM
HM_category_products
WHERE
HM_category_products.category_id IN (SELECT
HM_categories.`id`
FROM
HM_categories
WHERE
(id = c.`id` OR id = c.`parent_id`))) AS count
FROM
`HM_categories` AS c
EDITED :- Below is my tables structure. This is just an example.
Category Table
id parent_id name slug enabled
1 0 Mobiles & Tablets mobiles-tablets 1
2 1 Mobile Phones mobile-phones 1
3 1 Tablets tablets 1
4 1 Mobile Accessories mobile-accessories 1
5 0 Electronics & Computers electronics-computers 1
6 5 Cameras & Accessories cameras-accessories 1
7 5 TV - Video - Audio tv-video-audio 1
Category Product Table
product_id category_id
1 2
2 2
3 2
4 2
5 3
6 2
7 3
8 3
9 3
10 2
11 3
12 2
13 2
14 2
15 2
You hav to use the "Group by" with something like:
SELECT
category_id, COUNT(*)
FROM
HM_category_products
GROUP BY category_id
This would get your table HM_category_products Grouped by category_id so will know how mane rows of each category its in the table, whats mean you will know the number of product of each category. Then you can join this resulting table with category one to get the category info. (Sorry for my english)
The GROUP BY statement is used in conjunction with the aggregate
functions to group the result-set by one or more columns. SQL GROUP BY Statement
for more info abaut "Group by" read
12.16.2 GROUP BY Modifiers and
12.16.1 GROUP BY (Aggregate) Functions
EDIT: I see now what you whant. I already give you the direction but here its a step furder: DISCLAIMER: THIS QUERY ITS JUST EXAMPLE, IT DOSNT WORK
CREATE VIEW view_2 AS
SELECT
category_id, COUNT(*) AS product_sum
FROM
HM_category_products
GROUP BY category_id
CREATE VIEW view_1 AS
SELECT
*
FROM
HM_categories
LEFT JOIN
view_2 AS a ON HM_categories.id = a.category_id;
SELECT
id,
name,
(SELECT
SUM(product_sum)
FROM
view_1
WHERE
parent_id = final.id) as product_count
FROM
HM_categories AS final;
that way you will get the product of a parent category, your only missing a CASE on the last select "product_count" to the child categorys, but that sum its easy because you already hav it on the view_1 (again sorry for my english)
Assume I have 4 tables:
Table 1: Task
ID Task Schedule
1 Cut Grass Mon
2 Sweep Floor Fri
3 Wash Dishes Fri
Table 2: Assigned
ID TaskID (FK) PersonID (FK)
1 1 1
2 1 2
3 2 3
4 3 2
Table 3: Person
ID Name
1 Tom
2 Dick
3 Harry
Table 4: Mobile
ID PersonID (FK) CountryCode MobileNumber
1 1 1 555-555-5555
2 2 44 555-555-1234
3 3 81 555-555-5678
4 3 81 555-555-0000
I'm trying to display the
Task on a certain day
Name of person assigned to task
Phone numbers of said person
I think it should be something like the following, but I'm not sure how to set up the conditions so that the results are limited correctly:
SELECT T.ID, T.Task, P.Name, M.MobileNumber
FROM Task AS T
LEFT JOIN Assigned AS A
ON T.ID = A.TaskID
LEFT JOIN Person AS P
ON A.PersonID = P.ID
LEFT JOIN Mobile AS M
ON M.PersonID = P.ID
WHERE T.Schedule = Fri
My goal is to fetch the following information (it will be displayed differently):
Tasks Name MobileNumber
Sweep Floor, Wash Dishes Dick, Harry 44-555-555-1234, 81-555-555-5678, 81-555-555-0000
Of course, if JOIN is the wrong way to do this, please say so.
It's unclear what you want to do with duplicate data in this case, but you should be looking at using inner joins instead of outer joins, and using something like group_concat() to combine the phone numbers.
I have three tables that hold items like:
Products:
ID NAME CATEGORY STOCK
1 Bolts 3 1
2 Daisies 4 1
3 Milk 5 2
4 Washers 3 3
5 Roses 4 1
Categories:
ID DESCRIPTION
3 Hardware
4 Plants
5 Food
Stocks:
ID DESCRIPTION
1 In Stock
2 Out of Stock
3 Ordered
I've been banging my head to get an SQL statement that will return a percentage of my items that are in stock based on their category, but I just can't make it work.
I'm looking for a statement that will return something like:
CATEGORY PERCENTAGE // comments
Hardware 50 // Bolts in stock but washers are ordered
Plants 100 // all plants in stock
Food 0 // milk is out of stock
Any ideas...?
select DESCRIPTION, sum(STOCK = 1) / count(*) as PERCENTAGE
from Products p
join Categories c on c.id = p.CATEGORY
group by DESCRIPTION
This works because STOCK = 1 is a boolean, which is 1 if true and 0 if false, so SUM(STOCK = 1) counts how many times STOCK = 1 is true!
I can't really see the use of this statement, but it would be
SELECT c.DESCRIPTION, count(p.STOCK = 1) / count(*) * 100
FROM CATEGORY c
JOIN PRODUCT p ON p.CATEGORY = c.ID
GROUP BY c.ID, c.DESCRIPTION
Should do it.