I'm fairly new to php / mysql programming and I'm having a hard time figuring out the logic for a relational database that I'm trying to build. Here's the problem:
I have different leaders who will be in charge of a store anytime between 9am and 9pm.
A customer who has visited the store can rate their experience on a scale of 1 to 5.
I'm building a site that will allow me to store the shifts that a leader worked as seen below.
When I hit submit, the site would take the data leaderName:"George", shiftTimeArray: 11am, 1pm, 6pm (from the example in the picture) and the shiftDate and send them to an SQL database.
Later, I want to be able to get the average score for a person by sending a query to mysql, retrieving all of the scores that that leader received and averaging them together. I know the code to build the forms and to perform the search. However, I'm having a hard time coming up with the logic for the tables that will relate the data. Currently, I have a mysql table called responses that contains the following fields,
leader_id
shift_date // contains the date that the leader worked
shift_time // contains the time that the leader worked
visit_date // contains the date that the survey/score was given
visit_time // contains the time that the survey/score was given
score // contains the actual score of the survey (1-5)
I enter the shifts that the leader works at the beginning of the week and then enter the survey scores in as they come in during the week.
So Here's the Question: What mysql tables and fields should I create to relate this data so that I can query a leader's name and get the average score from all of their surveys?
You want tables like:
Leader (leader_id, name, etc)
Shift (leader_id, shift_date, shift_time)
SurveyResult (visit_date, visit_time, score)
Note: omitted the surrogate primary keys for Shift and SurveyResult that I would probably include.
To query you join shifts and surveys group on leader and taking the average then jon that back to leader for a name.
The query might be something like (but I haven;t actually built it in MySQL to verify syntax)
SELECT name
,AverageScore
FROM Leader a
INNER JOIN (
SELECT leader_id
, AVG(score) AverageScore
FROM Shift
INNER JOIN
SurveyResult ON shift_date = visit_date
AND shift_time = visit_time --depends on how you are recording time what this really needs to be
GROUP BY leader ID
) b ON a.leader_id = b.leader_id
I would do the following structure:
leaders
id
name
leaders_timetabke (can be multiple per leader)
id,
leader_id
shift_datetime (I assume it stores date and hour here, minutes and seconds are always 0
survey_scores
id,
visit_datetime
score
SELECT l.id, l.name, AVG(s.score) FROM leaders l
INNER JOIN leaders_timetable lt ON lt.leader_id = l.id
INNER JOIN survey_scores s ON lt.shift_datetime=DATE_FORMAT('Y-m-d H:00:00', s.visit_datetime)
GROUP BY l.id
DATE_FORMAT here helps to cut hours and minutes from visit_datetime so that it could be matched against shift_datetime. This is MYSQL function, so if you use something else you'll need to use different function
Say you have a 'leader' who has 5 survey rows with scores 1, 2, 3, 4 and 5.
if you select all surveys from this leader, sum the survey scores and divide them by 5 (the total amount of surveys that this leader has). You will have the average, in this case 3.
(1 + 2 + 3 + 4 + 5) / 5 = 3
You wouldn't need to create any more tables or fields, you have what you need.
Related
I'm trying to build a reporting table to track server traffic and popularity overall. Each SID is a unique game server hosting a particular game, and each UCID is a unique player key connecting to that server.
Say I have a table like so:
SID UCID AvgTime NumConnects
-----------------------------------------
1 AIE9348ietjg 300.55 5
1 Po328gieijge 500.66 7
2 AIE9348ietjg 234.55 3
3 Po328gieijge 1049.88 18
We can see that there are 2 unique players, and 3 unique servers, with SID 1 having 2 players that have connected to it at some point in the past. The AvgTime is the average amount of time those players spent on that server (in seconds), and the NumConnects is the size of the average (ie. 300.55 is averaged out of 5 elements).
Now I run a job in the background where I process a raw connection table and pull out player connections like so:
SID UCID ConnectTime DisconnectTime
-----------------------------------------
1 AIE9348ietjg 90.35 458.32
2 Po328gieijge 30.12 87.15
2 AIE9348ietjg 173.12 345.35
This table has no ID or other fluff to help condense my example. There may be multiple connect/disconnect records for multiple players in this table. What I want to do is add to my existing AvgTime for each SID these new values.
There is a formula from here I am trying to use (taken from this math stackexchange: https://math.stackexchange.com/questions/1153794/adding-to-an-average-without-unknown-total-sum/1153800#1153800)
Average = (Average * Size + NewValue) / Size + 1
How can I write an update query to update each ServerIDs traffic table above, and add to the average using the above formula for each pair of records. I tried something like the following but it didn't work (returned back null):
UPDATE server_traffic st
LEFT JOIN connect_log l
ON st.SID = l.SID AND st.UCID = l.UCID
SET AvgTime = (AvgTime * NumConnects + SUM(l.DisconnectTime - l.ConnectTime) / NumConnects + COUNT(l.UCID)
I would prefer an answer in MySql, but I'll accept MS SQL as well.
EDIT
I understand that statistics and calculations are generally not to be stored in tables and that you can run reports that would crunch the numbers for you. My requirement is that users can go to a website and view the popularity of various servers. This needs to be done in a way that
A: running a complex query per user doesn't crash or slow down the system
B: the page returns the data within a few seconds at most
See this example here: https://bf4stats.com/pc/shinku555555
This is a web page for battlefield 4 stats - notice that the load is almost near instant for this player, and I get back a load of statistics without waiting for some complex report query to return the data. I'm assuming they store these calculations in preprocessed tables where the webpage just needs to do a simple select to return back the values. That's the same approach I want to take with my Database and Web Application design.
Sorry if this is off topic to the original question - but hopefully this adds additional context that helps people understand my needs.
Since you cannot run aggregate functions like SUM and COUNT by themselves at the unit level in SQL but contained in an aggregate query, consider joining to an aggregate subquery for the UPDATE...LEFT JOIN. Also, adjust parentheses in SET to match above formula.
Also, note that since you use LEFT JOIN, rows with non-match IDs will render NULL for aggregate fields and this entity cannot be used in arithmetic operations and will return NULL. You can convert to zero with IFNULL() but may fail with formula's division.
UPDATE server_traffic s
LEFT JOIN
(SELECT SID, UCID, COUNT(UCID) As GrpCount,
SUM(DisconnectTime - ConnectTime) AS SumTimeDiff
FROM connect_log
GROUP BY SID, UCID) l
ON s.SID = l.SID AND s.UCID = l.UCID
SET s.AvgTime = (s.AvgTime * s.NumConnects + l.SumTimeDiff) / s.NumConnects + l.GrpCount
Aside - reconsider saving calculations/statistics within tables as they can always be run by queries even by timestamps. Ideally, database tables should store raw values.
I'm struggling with an SQL query.
I am building a booking system for a ski resort and in my database I have instructors and sessions. A session can have an instructor, and it has a date and startTime and endTime.
In order to add a session, I want to get all available instructors for a chosen time and date. In other words, all instructors who don't have a booking on that date and at that time.
Table example:
e.g
instructors: i1, i2, i3, i4, i5, i6, i7, i8
sessions:
Instructor | date | start | end |
**i1** **2017-05-03** **14:30:00** **15:30:00**
**i2** **2017-05-03** **14:30:00** **15:30:00**
**i3** **2017-10-03** **10:30:00** **11:30:00**
**i4** **2017-05-03** **10:30:00** **11:30:00**
**i1** **2017-11-03** **14:30:00** **15:30:00**
Then for input date='2017-05-03' and start='14:30' and end='15'30' i want to get
i3,i4,i5,i6,i7,i8
Figured out that I need to left join session to instructors, group by instructor id and then eliminate those ids that have a field in the group with the selected
inputs. However, for the GROUP BY clause, i have to use an aggregate function and i don't know which one could apply here.
SirWinning's self-answer looks like it should work, but my version below removes some parts which weren't required.
select *
from instructor
where id not in
(select instructorid
from Session
where date='2017-03-19' and starttime<='15:30:00' and endtime>='14:30:00')
This code will find any instructors who aren't booked for a session which overlaps the 14:30-15:30 window on the relevant date.
If that's what's wanted, then you're good to go. Of course it doesn't follow that the instructor is "really available". There could be other things which affect their availabilty (working hours, annual leave etc), so you'll need to ensure that there are things in place to handle such things.
Note also, that this code will prevent an instructor appearing available for "back to back" bookings. If you want to allow a booking to start at 14:30 when another one ends at that time, you'll need to change the <= and >= to < and >.
using not exists()
select *
from instructors i
where not exists (
select 1
from sessions s
where s.instructor = i.id
and s.date = '2017-05-03'
and s.start = '14:30'
and s.end = '15:30'
)
So I tried this query and apparently it works(at least for my test case)
Can anybody take a look and tell me if it looks correct?
select *
from instructor
where id in
(select id
from instructor
group by id
having id not in
(select distinct(instructorid) from Session
where date='2017-03-19' and starttime<='15:30:00' and endtime>='14:30:00') )
I am trying to produce a query that will generate a list of absent students whenever a my code is typed. The problem I am running into is that the output list is displaying none of the names of the students that were in class. My goal is to only list students that are over 30 days according to their most recent recorded date of attendance. Students that are not over 30 days will not be shown at all. It seems pretty simple enough however I'm running into a block. Is there a Syntax or two that I am missing?
SELECT trim(concat(name.fname,' ' ,name.mname,' ',name.lname)) as student, name.noiid as stuID, sum(meeting.meefoiid) as NO_CLASS, squadlt.ltfname as Squad
FROM name
LEFT JOIN meeting ON name.foiid = meeting.meefoiid
LEFT JOIN squadlt ON name.squadlt = squadlt.ltid
WHERE meeting.meefoiid IS NULL
AND MEEDATE >= '2014-09-12'
AND name.city = 'RICHMOND'
GROUP BY student
ORDER BY name.squadlt, student;
I'm currently working on a league systeme for my sport team. A ladder, as seen as in some video games.
It's a mobile web site, allowing coaches to create games, and monitor players performances.
I have games automatically balanced, taking into accounts player's experiences and points, then, i give bonus points to the all the players of the winner team, and remove points from the losers.
I have a relatively simple database. 3 tables.
User : id - name
Games : id - ETA - cration_date
game_joueur: id- id_game - id_joueur - team - result - bonus
game_joueur beeing an assoc table, in wich i register for each new game players id, the team he has been seeded on, and afterwards, update the bonus field with the points earned and the result field with an integer (1 = lose, 2= win)
That way i can sum the bonus on my players stat and get the total points.
You can have a better look at the table here :
http://sqlfiddle.com/#!2/d3e06/2
What i'm tryng to acomplish is for each player's stat page, retrieve from the database the name of his most succesfull partner( the guy wich whom he won the most games), and also his worst ally , the men he lost the most match with.
This is what i do on my user stat page :
SELECT
(SELECT COUNT(lad_game_joueur.result) FROM lad_game_joueur WHERE result = 1 AND lad_game_joueur.id_joueur = lad_user.id) as lose,
(SELECT SUM(lad_game_joueur.bonus) FROM lad_game_joueur WHERE lad_game_joueur.id_joueur = lad_user.id) as points,
lad_user.id as id ,
(SELECT COUNT(lad_game_joueur.result) FROM lad_game_joueur WHERE lad_game_joueur.id_joueur = lad_user.id AND result =2) as win,
lad_user.name
FROM lad_user,lad_game_joueur
WHERE lad_game_joueur.id_joueur = lad_user.id AND lad_user.id
='.$id_joueur.'
GROUP BY lad_user.id
ORDER BY puntos DESC
I'm sure this is not the best way to do it, but it works :) ( i'm no sql specialist)
How can i tune this query to also retrive the informations i'm looking for?
I wont mind doing another query.
Thanks a lot in advance!
Ben
Ok i finealy found a way.
Here's what i did :
SELECT
SUM(result)as result_sum, sum(Bonus) as bonus_sum, id_joueur
from lad_game_joueur
where result= 2
and id_game in
(SELECT lad_game_joueur.id_game from lad_game_joueur,lad_game where id_joueur=2
AND result= 2 and lad_game_joueur.id_game=lad_game.id)
group by id_joueur
order by result_sum DESC, bonus_sum desc
As you see, the sum of result would give me 4 if i won two games with the person, but i just divide by 2 on php and voilà :)
I own an online game in which you become the coach of a rugby team and I recently started to optimize my database. The website uses CodeIgniter framework.
I have the following tables (the tables have more fields but I posted only those which are important now):
LEAGUES: id
STANDINGS: league_id, team_id, points
TEAMS: id, active
Previously, I was having in the LEAGUES table a field named teams. This was representing the number of active teams in that league (of which users logged in recently).
So, I was doing the following select to get a random league that has between 0 and 4 active teams (leagues with less teams first).
SELECT id FROM LEAGUES WHERE teams>0 AND teams<4 ORDER BY teams ASC, RAND( ) LIMIT 1
Is there any way I can do the same command now without having to add the teams field?
Is it efficient? Or It's better to keep the teams field in the database?
LATER EDIT
This is what I did until now:
function test()
{
$this->db->select('league_id, team_id');
$this->db->join('teams', 'teams.id = standings.team_id');
$this->db->where('active', 0);
$query = $this->db->get('standings');
return $query->result_array();
}
The function returns all inactive teams alongside with their league_id.
Now how do I count the number of inactive teams in each league and how to I sort them after this number?
Try this:
select league_id
from standings s
join teams t on t.id = s.team_id and t.active
group by 1
having count(*) < 5