I have the following table
coaches( coach_code, coach_name, year_of_birth)
I need to create a query that returns pairs of coaches that were born at the same year and the year. every pair should appear only once. (coach 1, coach 2,year_of_birth)
the problem is that it's the same table and the inner join doesn't work.
any suggestions ?
SELECT c1.coach_code AS coach1, c2.coach_code AS coach2, c1.year_of_birth
FROM coaches AS c1
JOIN coaches AS c2 ON c1.year_of_birth = c2.year_of_birth AND c1.coach_code < c2.coach_code
You can use GROUP_CONCAT but keep in mind there is limit of characters in GROUP_CONCAT
SELECT GROUP_CONCAT(coach_name SEPARATOR ',') as `pair`,year_of_birth
FROM coaches
GROUP BY year_of_birth
GROUP_CONCAT(expr)
Related
I encountered a problem on a database I am working with. I have a table of counsels which may hold repeating values, but their is an enrolment number filed which is unique and can be used to fetch them. However, I want to join from a cases_counsel table on the "first" unique value of the counsel table that matches that column on the cases counsel table.
I want to list the cases belonging to a particular counsel using the enrolment_number as the counsel_id on the cp_cases_counsel table. That means I want to pick just a distinct value of a counsel, then use it to join the cp_cases_counsel table and also return the count for such.
However, I keep getting duplicates. This was the mysql query I tried
SELECT T.suitno, T.counsel_id, COUNT(*) as total from cp_cases_counsel T
INNER JOIN (SELECT
enrolment_number as id, MIN(counsel)
FROM
cp_counsel
GROUP BY
enrolment_number
) A
ON A.id = T.counsel_id
GROUP BY T.suitno, T.counsel_id
and
SELECT enrolment_number as id, MIN(counsel) as counsel, COUNT(*) as total FROM cp_counsel
JOIN cp_cases_counsel ON cp_cases_counsel.counsel_id = cp_counsel.enrolment_number
GROUP BY enrolment_number
For the second query, it's joining twice and I am having like double of what I am supposed to get.
The columns that you want in the results are councel (actually only one of all its values) from cp_counsel and counsel_id from cp_cases_counsel, so you must group by them and select them:
SELECT a.counsel, t.counsel_id, COUNT(*) AS total
FROM cp_cases_counsel t
INNER JOIN (
SELECT enrolment_number, MIN(counsel) AS counsel
FROM cp_counsel
GROUP BY enrolment_number
) a ON a.enrolment_number = t.counsel_id
GROUP BY a.counsel, t.counsel_id;
I want to get the each count of data by combining two tables in MySQL. This is the scenario I have following tables. emp_tab(name, dept_id ) and dept_tab(dept_id, dept_name). I want to write a query to show the number of employees in each department with the department name.
tried code:
SELECT dept_tab.dept_name, number
FROM emp_tab
INNER JOIN dept_tab ON emp_tab.dept_id=dept_tab.dept_id;
My try is not successful. Can you please show me how can I solve this. I am beginner to MySQL
Two things:
You need to use a group by and count function
Your join was joining an invalid table
SELECT dept_tab.dept_name, COUNT(*) as number
FROM emp_tab
INNER JOIN dept_tab ON emp_tab.dept_id=dept_tab.dept_id
GROUP BY dept_tab.dept_name
You can use JOIN and GROUP BY by dept_name to count number of employees.
In your question, what is Customerstable? I assume that is dept_tab?
SELECT
d.dept_name,
COUNT(d.id) AS cnt
FROM
dept_tab d
LEFT JOIN empt_tab e
ON e.dept_id = d.dept_id
GROUP BY d.dept_name ;
I tried to write a query, but unfortunately I didn't succeed.
I want to know how many packages delivered over a given period by a person.
So I want to know how many packages were delivered by John (user_id = 1) between 01-02-18 and 28-02-18. John drives another car (another plate_id) every day.
(orders_drivers.user_id, plates.plate_name, orders.delivery_date, orders.package_amount)
I have 3 table:
orders with plate_id delivery_date package_amount
plates with plate_id plate_name
orders_drivers with plate_id plate_date user_id
I tried some solutions but didn't get the expected result. Thanks!
Try using JOINS as shown below:
SELECT SUM(o.package_amount)
FROM orders o INNER JOIN orders_drivers od
ON o.plate_id=od.plate_id
WHERE od.user_id=<the_user_id>;
See MySQL Join Made Easy for insight.
You can also use a subquery:
SELECT SUM(o.package_amount)
FROM orders o
WHERE EXISTS (SELECT 1
FROM orders_drivers od
WHERE user_id=<user_id> AND o.plate_id=od.plate_id);
SELECT sum(orders.package_amount) AS amount
FROM orders
LEFT JOIN plates ON orders.plate_id = orders_drivers.plate_id
LEFT JOIN orders_driver ON orders.plate_id = orders_drivers.plate_id
WHERE orders.delivery_date > date1 AND orders.delivery_date < date2 AND orders_driver.user_id = userid
GROUP BY orders_drivers.user_id
But seriously, you need to ask questions that makes more sense.
sum is a function to add all values that has been grouped by GROUP BY.
LEFT JOIN connects all tables by id = id. Any other join can do this in this case, as all ids are unique (at least I hope).
WHERE, where you give the dates and user.
And GROUP BY userid, so if there are more records of the same id, they are returned as one (and summed by their pack amount.)
With the AS, your result is returned under the name 'amount',
If you want the total of packageamount by user in a period, you can use this query:
UPDATE: add a where clause on user_id, to retrieve John related data
SELECT od.user_id
, p.plate_name
, SUM(o.package_amount) AS TotalPackageAmount
FROM orders_drivers od
JOIN plates p
ON o.plate_id = od.plate_id
JOIN orders o
ON o.plate_id = od.plate_id
WHERE o.delivery_date BETWEEN convert(datetime,01/02/2018,103) AND convert(datetime,28/02/2018,103)
AND od.user_id = 1
GROUP BY od.user_id
, p.plate_name
It groups rows on user_id and plate_name, filter a period of delivery_date(s) and then calculate the sum of packageamount for the group
The following query works great
SELECT
t.name,
t.id
FROM
team t,
member m
WHERE
m.team_id = t.id
and shows multiple results
what I am stuck with it is with how to modify the query about to display the team name and the number of team members in that team so, for example, Team A has 50 team members, Team B has 20 members and so on.
The problem is that the member.team_id has Comma separated values
My table structure for team table
My table structure for member table
Not a duplicate question at all
Use the technique in sql join tables where 1 column has comma to join the tables, then use COUNT(*) to get the member counts.
SELECT t.name, COUNT(*)
FROM team t
JOIN member m
ON FIND_IN_SET( m.team_id, t.id ) > 0
GROUP BY t.name
To get the number of members from comma separated list try using length() and replace()
select
(LENGTH(team_ids) - LENGTH(REPLACE(team_ids, ',', '')))+1
from MyTable
By removing the commas the length is reduced by the number of those, and ou need 1 more because there isn't a trailing comma at the end.
I have two tables - one for courses and one for people attending the course.
Both are joined by course_id
table 1: firstaid - has all the course names
table 2: first_aid_att - records attendees and captures first aid
course id
I would like to get a count of attendees per course.
I have got a join working but don't know how to do the group by and count.
SELECT *
FROM firstaid
LEFT JOIN first_aid_att ON firstaid.course_id = first_aid_att.course_id
ORDER BY `sortDate` ASC
Try this:
SELECT f1.*, COUNT(f2.course_id)
FROM firstaid f1
LEFT JOIN first_aid_att f2 ON (f1.course_id = f2.course_id)
GROUP BY f1.course_id
ORDER BY f2.sortDate