I have a track and Field Database with these tables (simplified):
Performance Table
Row Athlete Event Mark Meet
1 1 3 0:55 A
2 2 2 2:25 A
3 3 3 0:54 A
4 4 4 4:10 A
5 2 2 2:11 A
6 3 2 2:12 B
7 1 1 10 C
Athlete Table
Row Name Age Sex
1 Joe 13 M
2 Amy 15 F
3 John 16 M
4 Tim 17 M
So I understand how to implement this for an event with only 1 athlete (e.g. 100 m dash), but how would I include a relay event with 4 athletes. So, for example a 4x400 relay would need 4 athletes. In other words, some events have only 1 athlete and some have more than one. I am not sure if I should use:
Linking Table
Add 4 Columns
Do a table like below.
Other
Option 3 Table
Performance Table (Event 5 is a relay)
Row Athlete Event Mark Meet
1 1 3 0:55 A
2 2 2 2:25 A
3 3 3 0:54 A
4 4 4 4:10 A
5 2 2 2:11 A
6 3 2 2:12 B
7 1 5 9:34 C
8 2 5 9:34 C
9 3 5 9:34 C
10 4 5 9:34 C
Are you going to have events in the system before they are finished? For example, today's meet will include a 4x400 and here are the runners...
If that's the case then you'll need the linking table that you referred to because you want to be able to have that data stand on its own. It would just have the event_id and athlete_id in it so that you could have that set up. That would also be the PK (Primary Key) for the table and you would then use those two columns as the FK (Foreign Key) to the Performance table that you have at the end. If the data will never exist without times then you could just skip the link table and have the Performance table, although having the link table still wouldn't hurt in that case.
Related
I'm studying SQL and somehow I'm stuck with a question. I have 2 tables ('users' and 'follows').
Follows Table
user_id
follows
date
1
2
1993-09-01
2
1
1989-01-01
3
1
1993-07-01
2
3
1994-10-10
3
2
1995-03-01
4
2
1988-08-08
4
1
1988-08-08
1
4
1994-04-02
1
5
2000-01-01
5
1
2000-01-02
5
6
1986-01-10
7
1
1990-02-02
1
7
1996-10-01
1
8
1993-09-03
8
1
1995-09-01
8
9
1995-09-01
9
8
1996-01-10
7
8
1993-09-01
3
9
1996-05-30
4
9
1996-05-30
Users Table
user_id
first_name
last_name
school
1
Harry
Potter
Gryffindor
2
Ron
Wesley
Gryffindor
3
Hermonie
Granger
Gryffindor
4
Ginny
Weasley
Gryffindor
5
Draco
Malfoy
Slytherin
6
Tom
Riddle
Slytherin
7
Luna
Lovegood
Ravenclaw
8
Cho
Chang
Ravenclaw
9
Cedric
Diggory
Hufflepuff
I need to list all rows from follows where someone from one house follows someone from a different house. I tried to make 2 queries, one to get all houses related to follows.user_id and another one with all houses related to follows.follows and "merge" then:
select a.nome_id, a.user_id_house, b.follows_id, b.follows_house
from ( select follows.user_id as nome_id
, users.house as user_id_house
from follows inner join users
ON users.user_id = follows.user_id
) as a,
( select follows.follows as follows_id
, users.house as follows_house
from follows inner join users
ON follows.user_id = users.user_id
) as b
where a.user_id_house <> b.follows_house;
The problem is that the result is like 400 rows, its not right. I have no idea how I could solve this.
Try this
SELECT follows.user_id, users.school, followers.user_id, followers.school FROM follows
JOIN users ON follows.user_id=users.user_id
JOIN users as followers ON follows.follows=followers.user_id
WHERE users.school <> followers.school
Note: Pay attention to naming in my answer
Thanks for correcting to Thorsten Kettner
I have a requirement from client where I need to store a value against list of combination.
For example I have following LOBs and against each combination I need to store a value.
Auto
WC
Personal
I purposed multiple solutions he is not satisfied with anyone.
Solution 1: create single table, insert value against all possible combination(string) something like
LOB Value
Auto 1
WC 2
Personal 3
Auto,WC 4
Auto, personal 5
WC, Personal 6
Auto, WC, Personal 7
Solution 2: create lkp_lob, lob_group and lob_group_detail tables. Each group combination represent a group.
Lkp_lob
Lob_key Name
1 Auto
2 WC
3 Person
Lob_group (unique query constrain on lob_group_key and lob_key)
Lob_group_key Lob_key
1 1
2 2
3 3
4 1
4 2
5 1
5 3
6 2
6 3
7 1
7 2
7 3
Lob_group_detail
Lob_group_key Value
1 1
2 2
3 3
4 4
5 5
6 6
7 7
Any suggestion would be highly appreciated.
First of all I did not understood that terms you said.
But from database perspective it is always good to have multiple tables for each module. You will be facing less difficulties when doing CRUD. And will be more faster.
My company sends folks to training. Based on projected new hires/transfers, I was asked to generate a report that estimates the number of seats we need in each course broken out by quarter.
Question: My question is two-fold:
What is the best way to represent a sequence of courses (i.e. prerequisites) in a relational DB?
How do I create the query(-ies) necessary to produce the following desired output:
Desired Output:
ID PersonnelID CourseID ProjectedStartDate ProjectedEndDate
1 1 1 1/14/2017 1/14/2017
2 2 1 2/17/2017 2/17/2017
3 2 2 2/18/2017 2/19/2017
4 2 3 2/20/2017 2/20/2017
5 3 49 1/18/2017 2/03/2017
6 …
Background Info: The courses are taken in-sequence: the first few courses are orientation courses for the company, and later courses are more specific to the employee's workrole. There are over 50 different courses, 40 different workroles and we're projecting ~1k new hires/transfers. Each work role must take a sequence of courses in a prescribed order, but I'm having trouble representing this ordering and subsequently writing the necessary query.
Existing Tables:
I have several tables that I've used to store the data: Personnel, LnkPersonnelToWorkroles,Workroles, LnkWorkrolesToCourses, and Courses (there's many others as well, but I omit them for the sake of scoping this question down). Here's some notional data from these tables:
Personnel (These are the projected new hires and their estimated arrival date.)
ID DisplayName RequiredCompletionDate
1 Kristel Bump 10/1/2016
2 Shelton Franke 3/11/2017
3 Shaunda Launer 4/16/2017
4 Clarinda Kestler 3/13/2017
5 My Wimsatt 6/6/2017
6 Gillian Bramer 10/25/2016
7 ...
Workroles (These are the positions in the company)
ID Workrole
1 Manager
2 Secretary
3 Admin Asst.
4 ...
LnkPersonnelToWorkroles (Links projected new hires to their projected workrole)
ID PersonnelID WorkroleID
1 1 1
2 2 1
3 3 1
4 4 1
5 5 1
6 6 1
7 ...
Courses (All courses available)
ID CourseName LengthInDays
1 Orientation 1
2 Email Etiquette 2
3 Workplace Safety 1
4 ...
LnkWorkrolesToCourses
(Links workroles to their required courses in a Many-to-Many relationship)
ID WorkroleID CourseID
1 1 1
2 2 1
3 2 2
4 2 3
5 3 49
6 ...
Thoughts: My approach is to first develop a person-by-person schedule based upon the new hire's target completion date and workrole. Then for each class, I could sum the number of new hires starting in that quarter.
I've considered trying to represent the courses in the most general way I could think of (i.e. using a directed acyclic graph), but since most of the courses have only a single prerequisite course, I think it's much easier to represent the prerequisites using the Prerequisites table below; however, I don't know how I would use this in a query.
Prerequisites (Is this a good idea?)
ID CourseID PrereqCourseID
1 2 1
2 3 1
3 4 1
4 5 4
5 ...
Note: I am not currently concerned with whether or not the courses are actually offered on those days; we will figure out the course schedules once we know approximately how many we need each quarter. Right now, we're trying to estimate the demand for each course.
Edit 1: To clarify the Desired Output table: if the person begins course 1 on day D, then they can't start course 2 until after they finish course 1, i.e. until the next day. For courses with a length L >1 days, the start date for a subsequent courses is delayed L days. Notice this effect playing out for workrole ID 2 in the Desired Output table: He is expected to arrive on 2/17, start and complete course 1 the same day, begin course 2 the next day (on 2/18), and finish course 2 the day after that (on 2/19).
I'm posting this answer because it gives me an approximate solution; other answers are still welcome.
I avoided a prerequisite table altogether and opted for a simpler approach: a partial ordering of the courses.
First, I drew the course prerequisite tree; it looked similar to this image:
I defined a partial ordering of the courses based on their depth in the prerequisite tree. In the picture above, CHM124 and High School Chem w/ Lab are priority 1, CHM152 is priority 2, CHM 153 is priority 3, CHM260 and CHM 270 are priority 4, and so on... This partial ordering was stored in the CoursePriority table:
CoursePriority:
ID CourseID Priority
1 1 1
2 2 2
3 3 3
4 4 3
5 5 4
6 6 3
7 ...
So that no two courses would every be taken at the same time, I perturbed each course's priority by a small random number using the following Update query:
UPDATE CoursePriority SET CoursePriority.Priority = [Priority]+Rnd([ID])/1000;
(I used [ID] as input to the Rnd method to ensure each course was perturbed by a different random number.) I ended up with this:
ID CourseID Priority
1 1 1.000005623
2 2 2.000094955
3 3 3.000036401
4 4 3.000052486
5 5 4.000076711
6 6 3.00000535
7 ...
The approach above answers my first question "What is the best [sensible] way to represent a sequence of courses (i.e. prerequisites) in a relational DB?" Now as for generating the course schedule...
First, I created a query qryLnkCoursesPriorities to link Courses to the CoursePriority table:
SELECT Courses.ID AS CourseID, Courses.DurationInDays, CoursePriority.Priority
FROM Courses INNER JOIN CoursePriority ON Courses.ID = CoursePriority.CourseID;
Result:
CourseID DurationInDays Priority
1 35 1.000076177
2 21 2.000148297
3 28 3.000094352
4 14 3.000081442
5...
Second, I created the qryWorkrolePriorityDelay query:
SELECT LnkWorkrolesToCourses.WorkroleID, qryLnkCoursePriorities.CourseID AS CourseID, qryLnkCoursePriorities.Priority, qryLnkCoursePriorities.DurationInDays, ([DurationInDays]+Nz(DSum("DurationInDays","qryLnkCoursePriorities","[Priority]>" & [Priority] & ""))) AS LeadTimeInDays
FROM LnkWorkrolesToCourses INNER JOIN qryLnkCoursePriorities ON LnkWorkrolesToCourses.CourseID = qryLnkCoursePriorities.CourseID
ORDER BY LnkWorkrolesToCourses.WorkroleID, qryLnkCoursePriorities.Priority;
Simply put: The qryWorkrolePriorityDelay query tells me how many days in advance each course should be taken to ensure the new hire can complete all subsequent courses prior to their required training completion deadline. It looks like this:
WorkroleID CourseID Priority DurationInDays LeadTimeInDays
1 7 1.000060646 7 147
1 1 1.000076177 35 140
1 2 2.000148297 21 105
1 4 3.000081442 14 84
1 6 3.000082824 14 70
1 3 3.000094352 28 56
1 5 4.000106905 28 28
2...
Finally, I was able to bring this all together to create the qryCourseSchedule query:
SELECT Personnel.ID AS PersonnelID, LnkWorkrolesToCourses.CourseID, [ProjectedHireDate]-[leadTimeInDays] AS ProjectedStartDate, [ProjectedHireDate]-[leadTimeInDays]+[Courses].[DurationInDays] AS ProjectedEndDate
FROM Personnel INNER JOIN (((LnkWorkrolesToCourses INNER JOIN (Courses INNER JOIN qryWorkrolePriorityDelay ON Courses.ID = qryWorkrolePriorityDelay.CourseID) ON (Courses.ID = LnkWorkrolesToCourses.CourseID) AND (LnkWorkrolesToCourses.WorkroleID = qryWorkrolePriorityDelay.WorkroleID)) INNER JOIN LnkPersonnelToWorkroles ON LnkWorkrolesToCourses.WorkroleID = LnkPersonnelToWorkroles.WorkroleID) INNER JOIN CoursePriority ON Courses.ID = CoursePriority.CourseID) ON Personnel.ID = LnkPersonnelToWorkroles.PersonnelID
ORDER BY Personnel.ID, [ProjectedHireDate]-[leadTimeInDays]+[Courses].[DurationInDays];
This query gives me the following output:
PersonnelID CourseID ProjectedStartDate ProjectedEndDate
1 7 5/7/2016 5/14/2016
1 1 5/14/2016 6/18/2016
1 2 6/18/2016 7/9/2016
1 4 7/9/2016 7/23/2016
1 6 7/23/2016 8/6/2016
1 3 8/6/2016 9/3/2016
1 5 9/3/2016 10/1/2016
2...
With this output, I created a pivot table, where course start dates were grouped by quarter and counted. This gave me exactly what I needed.
Here is the info i have on my tables, what i need is to create a report based on certain dates and make a sum of every stock movement of the same id
Table one Table Two
Items Stocks
---------- ---------------------------
ID - NAME items_id - altas - bajas - created_at
1 White 4 5 0 8/10/2016
2 Black 2 1 5 8/10/2016
3 Red 3 3 2 8/11/2016
4 Blue 4 1 4 8/11/2016
2 10 2 8/12/2016
So based on a customer choice of dates (on this case lets say it selects all the data available on the table), i need to group them by items_id and then SUM all altas, and all bajas for that items_id, having the following at the end:
items_id altas bajas
1 0 0
2 11 7
3 3 2
4 6 4
Any help solving this?
Hope this will help:
Stock.select("sum(altas) as altas, sum(bajas) as bajas").group("item_id")
I am working with MS Access 2007. I have 2 tables: Types of Soda, and Likeability.
Types of Soda are: Coke, Pepsi, Dr. Pepper, and Mello Yellow
Likeability is a lookup with these options: Liked, Disliked, No preference
I know how to count the number of Cokes or Mello Yellows in the table using DCount("[Types]", "[Types of Soda]", "[Types]" = 'Coke')
I also know how to count the number of Liked, Disliked, No preference.
("[Perception]", "[Likeability]", "[Perception]" = 'Liked')
But, what if I need to count the number of "Likes" by Type.
i.e. the table should look like this:
Coke | Pepsi | Dr. Pepper | Mello Yellow
Likes 9 2 12 19
Dislikes 2 45 1 0
No Preference 0 12 14 15
I know in Access I can create a cross tab queries, but my tables are joined by an ID. So my [Likeability] table has an ID column, which is the same as the ID column in my [Types] table. That's the relationship, and that's what connects my tables.
My problem is that I don't know how to apply the condition for counting the likes, dislikes, etc, for ONLY the Types that I specify. It seems like I first have to check the [Likeability] table for "Likes", and cross reference the ID with the ID in the [Types] table.
I am very confused, and you may be too, now. But all I want to do is count the # of Likes and Dislikes for each type of soda.
Please help.
Its not really clear (to me anyway) what your tables look like so lets assume the following
tables
Soda
------
Soda_ID (Long Integer (Increment))
Soda_Name (Text(50)
Perception
------
Perception_ID (Long Integer (Increment))
Perception_Name (Text(50)
Likeability
-----------
Likeability_ID (Long Integer (Increment))
Soda_ID (Long Integer)
Perception_ID (Long Integer)
User_ID (Long Integer)
Data
Soda_Id Soda_Name
------- ---------
1 Coke
2 Pepsi
3 Dr. Pepper
4 Mello Yellow
Perception_ID Perception_Name
------------- ---------
1 Likes
2 Dislikes
3 No Preference
Likeability_ID Soda_ID Perception_ID User_ID
-------------- ------- ------------- -------
1 1 1 1
2 2 1 1
3 3 1 1
4 4 1 1
5 1 2 2
6 2 2 2
7 3 2 2
8 4 2 2
9 1 3 3
10 2 3 3
11 3 3 3
12 4 3 3
13 1 1 5
14 2 2 6
15 2 2 7
16 3 3 8
17 3 3 9
18 3 3 10
Transform query You could write a query like this
TRANSFORM
Count(l.Likeability_ID) AS CountOfLikeability_ID
SELECT
p.Perception_Name
FROM
Soda s
INNER JOIN (Perception p
INNER JOIN Likeability l
ON p.Perception_ID = l.Perception_ID)
ON s.Soda_Id = l.Soda_ID
WHERE
p.Perception_Name<>"No Preference"
GROUP BY
p.Perception_Name
PIVOT
s.Soda_Name;
query output
Perception_Name Coke Dr_ Pepper Mello Yellow Pepsi
--------------- ---- ---------- ------------ -----
Dislikes 1 1 1 3
Likes 2 1 1 1