I have to tables: Associates and Departments
One associate belongs to a department (belongs_to) and one department has many associates (has_many)
What I', trying to do is count number of associates on each department and make a pie chart with the data, i got the chart working with something basic (Department.count)
I just started with rails and I'm having issues with the query
Associate.joins(:department).group(:name).count
what i get is the following
Mysql2::Error: Column 'name' in field list is ambiguous: SELECT COUNT(*) AS count_all, name AS name FROM associates INNER JOIN departments ON departments.id = associates.department_id GROUP BY name
I tried doing a select, find and I just cant seem to get it right
If you have your associations setup correctly, I believe you should be able to do something like this:
Department.find(<some_id>).associates.count
Or if you have all the departments, and you're looping through them, let's say in a view and you want to get all the counts, you can do something like this:
#departments = Deparment.all
#departments.each do |department|
department.associates.count
end
You're associate table will need a department_id column on it.
As stated in the comment on your post, you have to resolve the ambiguous name attributed by specifying the table. You can do so either with the string as suggested, or by passing a block to group_by:
Associate.joins(:department).group_by(&:name).count
Related
I have table emails_grouping in that I have one column named 'to_ids' this column contains multiple employee Id's . Now I want to change that Id's with respective employee names. employee data is in employee table.
this is in mysql.
I tried multiple ways but I'm not able to replace id's with names because , that 'to_ids' column contains multiple 'Ids'.
description to_ids
'Inactive Employees with missing Last working day', '11041,11109,899,13375,1715,1026'
above is the column which I want to change Id's with employee names.
This problem should demonstrate to you why it's a bad idea to store "lists" of id's like you're doing. You should instead store one id per row.
You can join to your employee table like this:
SELECT e.name
FROM emails_grouping AS g
JOIN employee AS e
ON FIND_IN_SET(e.id, g.to_ids)
WHERE g.description = 'Inactive Employees with missing Last working day';
But be aware that joining using a function like this is not possible to optimize. It will have very slow performance, because it can't look up the respective employee id's using an index. It has to do a table-scan of the employee table, and evaluate the id's against your comma-separated list one by one.
This is just one reason why using comma-separated lists instead of normal columns is trouble. See my answer to Is storing a delimited list in a database column really that bad?
Suppose I have a database called clubmembership that has a column for names, a column for clubs, and a column for the role they play in that club. The name Margrit would be in the column name many times, or as many times as she is in a club. If I want to see which people are members of the sewing club my query might look something like this:
SELECT DISTINCT NAME FROM CLUBMEMBERSHIP
WHERE CLUB=’SEWING’
AND ROLE=’MEMBER’;
My problem is that I can't figure out a query for who is not in the sewing club. Of course the simple 'not in' clause isn't working because there are plenty of rows which sewing does not appear in. In this database if someone is not in the sewing club, sewing does not appear under club so I imagine there is a way to join the different rows with the same name under 'name' and then potentially use the 'not in' clause
I hope this was a good explanation of this question. I have been struggling with this problem for a while now.
Thanks for your help!
Nicolle
This is not something that can be solved by just changing the existing code, it is to do with the database design.
Database normalisation is the process of sorting out your database into sensible tables.
If you’re adding a person many times, then you should create a table called members instead. And if there is a list of clubs, then you should create a clubs table.
Then, you can create a table to join them together.
Here’s your three tables:
members
-------
id (int)
name (varchar)
clubs
-------
id (int)
name (varchar)
memberships
-------
member_id (int)
club_id (int)
Then you can use joins in MySQL to return the information you need.
Stack Overflow doesn’t like external links as the answer should be here, but this is a huge topic that won’t fit in a single reply, so I would briefly read about database normalization, and then read about ‘joining’ tables.
If I understand you correctly, you wanted to list all names that is not a member of SEWING. The Inner query will get all Names that are member of SEWING, however, the NOT EXISTS operator will get all Names that are not found in the inner query.
SELECT DISTINCT C.NAME
FROM CLUBMEMBERSHIP C
WHERE C.ROLE = 'MEMBER'
NOT EXISTS
(
SELECT NULL
FROM CLUBMEMBERSHIP D
WHERE D.CLUB='SEWING'
AND D.ROLE='MEMBER'
AND C.NAME = D.NAME
)
Here's a Demo.
I am trying to create a table that shows treatment information about patients (though I just wondered if would be better as a query) at a fictional hospital. The idea is that one row of this could be used to print an information sheet for the attending nurse(s).
I would like to make the attending_doctor column contain the name that corresponds with the employee_id.
|Patient_ID|Employee_ID|Attending_Doctor|Condition|Treatment|future_surgery|
Would appreciate any help. Thank you!
Just use a join in your query rather than have the employee name in 2 tables (which would mean updating in more than one location if they change name etc). For the sake of an example, this also gets the patients name from a 3rd table named patients.
eg
SELECT table1.*, employees.name, patients.name
FROM table1
LEFT JOIN employees ON employees.id = table1.employeeId
LEFT JOIN patients ON patients.id = table1.patientsId
Don't use directly this table, but build a view that contains the data you need. Then you can get the data from the view like it was a table.
Basically what you need is to have data in three tables. One table for patients, one table for for employees and one for the reports. Table with reports should contain only the employee_ID. Then you can either build a direct query over these three tables or build a view that will hide the complicated query.
This has been driving me mad.
I have three tables:
items
ID
name
type
cats
ID
name
items_to_cats
FK_ITEM_ID
FK_CAT_ID
This is a simple many-to-many relationship. I have items and categories. Each item can be linked to one or more categories. This is done via a simple joining table where each row maintains a relationship between one item and one category using foreign key constraints.
You will notice that my "items" table has a field called "type". This is an indexed column that defines the type of content stored there. Example values here are "report", "interview", "opinion", etc.
Here's the question. I want to retrieve a list of categories that have at least one item of type "report".
Ideally I want to get the result in a single query using joins. Help!
select distinct cats.id, cats.name
from cats
join items_to_cats on items_to_cats.fk_cat_id=cats.id
join items on items.id=items_to_cats.fk_item_id
where items.type='report'
Just as a point of database design, if you have a small set of legal values for items.type, i.e. "report", "interview", "opinion", maybe a couple more, then you really should create a separate table for that with, say, an id and a name, then just put the type id in the items table. That way you don't get into trouble because somewhere it's mis-spelled "raport", or even more likely, someone puts "reports" instead of "report".
or how about this :
SELECT c.id, c.name
FROM cats c
WHERE c.id IN
(SELECT ic.fk_cat_id
FROM items_to_cats ic
JOIN items i on i.id=ic.fk_item_id
WHERE items.type='report'
)
I have a bunch of records (orders) that I want to make available to users to make reports from.
The users come from different departments, and I would like to make it, so each department can only see their own stuff.
I can't figure out how to do this the right way.
What I have now is:
- A model where I have placed a Filter on the Order table.
The filter can use GetUserID() to get the users name, but I can't figure out how I get from that to the "UserDepartment" table that maps users to specific departments.
Ofcourse, I would prefer a solution whereby I didn't have to create new access groups or edit the model for each department that someone might dream up.
Any clues?
(Using SQL server 2008)
EDIT: This link http://blogs.msdn.com/bobmeyers/articles/Implementing_Data_Security_in_a_Report_Model.aspx shows the basics of what I'm trying to do, but the author seems to assume that each record have a UserName field that can be matched.
In my case i want all users of department X to be able to access the line.
We had a similar problem to this and ended up writing a function in SQL.
The function did the following:
Received the username parameter from SRSS
Performed a lookup on the permissions table and retrieved the records (department Id's in your case).
returned the department Id's
Then our sql statement looked like this:
SELECT *
FROM ImportantData
WHERE DepartmentId IN (SELECT Id FROM fn_GetUserDepartmentAllocations(#UserName))
This did force us to modify all of the sql queries but it allowed us to do it with minimal complex logic.
The other thing that this allows for is if you have one user who transcends department boundaries: for example a manager of 2 departments.
CREATE FUNCTION [dbo].[fn_GetUserDepartmentAllocations]
(
#UserName NVARCHAR(100)
)
RETURNS
#TempPermissions TABLE
(
DepartmentId Int
)
AS
BEGIN
INSERT INTO #TempPermissions
SELECT DepartmentId
FROM DepartmentPermissions
WHERE DepartmentAllowedUsername = #UserName
RETURN
END
The main benefit to doing it this way is it also allows you to edit one place to change the entire permissions structure, you don't have to go through each and every report to change it, instead you change one place
For example you could have a manager who belongs to 2 departments but is not allowed to view them except on thursdays (I know silly example but you get the point hopefully).
Hope this helps
Pete
This assume that Users have Orders.
So, filter by users who exist in the same dept as the filter user. Don't filter orders directly.
I've guessed at schema and column names: hoep you get the idea...
SELECT
MY STuff
FROM
Order O
JOIN
UserDept UD ON O.UserCode = UD.UserCode
WHERE
EXISTS (SELECT *
FROM
UserDept UD2
WHERE
UD2.UserCode = #MYUSerCode
AND
UD2.DeptID = UD.DeptID)
--or
SELECT
MY STuff
FROM
Order O
JOIN
UserDept D ON O.UserCode = D.UserCode
JOIN
UserDept U ON D.DeptID = U.DeptID
WHERE
U.UserCode = #MYUSerCode
What you're trying to achieve is difficult using the GetUserID() method. To use that your source query would have to return a lot of redundant data, imagine something like the following:
/*
Table: User
Fields: UserID, LoginName, FullName
Table: Department
Fields: DepartmentID, Name
Table: UserDepartments
Fields: UserID, DepartmentID
Table: Order
Fields: OrderNumber, DepartmentID
*/
SELECT O.OrderNumber, O.DepartmentID, U.LoginName
FROM Order O
JOIN Department D ON D.DepartmentID = O.DepartmentID
JOIN UserDepartments UD ON UD.DepartmentID = D.DepartmentID
JOIN User U ON U.UserID = UD.UserID
This will give you more rows than you want, basically a copy of the order for each user in the department that owns the order.
Now you can apply your filter as described in the link you provided. This will filter it down to just one copy of the order rows for the current user if they're in the right department.
If this is a performance issue there's other alternatives, easiest being using a local report (.RDLC) in either ASP.NET, WinForms or WPF and passing user details off to the data call so the filtering can be done in the SQL.