I have to create a database for a tool shop and since I am not able to get MySQL running, because of my computer, I wanted to ask for help with my queries.
I have several entities, like customer, car, repair, repair team member, employee, service, tire storage, personal file, sales.
Now I have to do following queries:
Sort every car that contains the combination "123" inside the vehicle identification number. (Result column: VehicleID)
Here I would say SELECT * FROM Vehicle WHERE VIN = '%123%';
A list of every sales in 2021. (Result column: document number)
Here I don't know how to connect both entities (service, sales) and filter by year.
The total revenue generated from sales in 2020
An overview of all the sales to the customer with the customer ID "4711" (Result column: Date of sale, product number, price)
What about -> SELECT * FROM Verkauf WHERE Verkauf.Dienstleistung_D_ID IN ( SELECT D_ID FROM Dienstleistung WHERE Kunde_K_ID == "K4711" )
Overview of all customers who have been sold something by an employee with employment year before 2010. The output should be sorted by last name and first name of the customer. (Result columns: Customer number, first name, last name, personnel number, last name of employee, year of employment).
I hope you can help me, since I am not able to create the code, even with SQLite, MySQL etc. so I am not able to test my queries and hope that you can help me.
ER Diagram
My ER diagram is in German, I hope you understand the structure.
Reparatur - repair,
Fahrzeug - car,
Kunde - customer ,
Dienstleistung - service,
Verkauf - sales ,
Reifenlagerung - tire storage,
Reparaturteammitglied - repair team member,
Mitarbeiter - employee,
Personalakte - personal file,
Related
I've 2 SQL tables:
The first is called LIVRAISON and stores all deliveries. It especially contains the customer's number (NumCptClient), date and time of the delivery (heureLiv, DateLiv) and the town name where the customer has been delivered (nomVille).
The second is called IMPERATIF that modelize a special service to clients wanting to be delivered before a given hour. That special service stands by a customer's number, a town name, the maximal hour when the customer must be delivered (heureImp) and start/end date of that premium option (dateDebImp, dateFinImp) : a delivery enters in the special service field when it matchs an IMPERATIF row by a NumCptClient AND nomVille combination and that its date is in the date range of that row (a customer, although having special service's orders, can be delivered in a town not concerned and vice versa: that kind of deliveries musn't be taken in account here).
I need to compute by a single and fast SQL query the rate between the number of deliveries that satisfied this special service (heureLiv <= heureImp) and the total number of deliveries for each couple of customer AND town concerned by this premium option.
I'd tailored that request that gives me all needed info except the rate:
SELECT NumCptCli, nomVille, heureImp, COUNT(*) AS TotalLivs
FROM LIVRAISON
NATURAL JOIN IMPERATIF
GROUP BY NumCptCli, nomVille
Then, the question is fondamentally, how to change that query so as to add a column with the corresponding rate, that is livsAlheure column below, and without display special service's couples that haven't any corresponding delivery registered yet?
NumCptCli |nomVille |heureImp|TotalLivs |livsAlheure
----------|--------------------|--------|----------|-----------
12345678 |PARIS |07:30 |311 |80.56
87654321 |BREST |15:30 |314 |95.2
...
My reservation system allows us to purchase credits for clients in terms of pre defined packages. I'm struggling with how I record and calculate available credits.
Let's say we're talking about a car wash service. A client can have multiple cars and can purchase the following services, 'Wash and Wax' and 'Detailing'.
Client 1 has two cars, Car A and Car B. He brings them both in and purchases:
Car A - 1 Wash and Wax
Car A - 1 Detailing
Car B - 10 Wash and Wax
Car B - 1 Detailing
This generates 4 rows in my Purchases table, one for each service purchased.
In my DB I have two related tables tracking purchases and reservations. Table 1 Purchases, Table 2 Reservations.
In Purchases I have the following fields of note:
id
client_id
car_id
service_id
credits_purchased
credits_scheduled
credits_used
cart_id
Then in my Reservation table I have the following fields of note:
id
client_id
car_id
service_id
reservation_date
completed_datetime
car_in_datetime
car_out_datetime
purchase_id
I track the credits available by updating the Purchases table fields credits_used and credits_on_schedule as events happen.
For example, when the client makes a reservation the system adds a new record in the Reservations table, once this happens the system also runs an update query and adds +1 to the related Purchases table credits_on_schedule. When the Reservation is updated to complete the system also updates the Purchases table and adds -1 to credits_on_schedule and +1 to credits used. Simple math between credits_purchased, credits_used, and credits_on_schedule derive what credits are available for a client to use.
I feel like this isn't a good way to track the credits. My question is what is a better implementation? Should I just track credits_purchased then use count queries on the Reservation table to calculate credits_used and credits_on_schedule? Should I be using a pivot table to track? I can't seem to wrap my head around what is the cleanest design.
It looks to me that the design is ok in general.
A reservation can only have one purchased related to it so purchase_id field is a foreign key in Reservation table.
Nevertheless, my advise to you is to create a log system of all these record updates.
As you mentioned, as events are fired the system updates the calculated fields.
What if for some reason the system fails at a certain point? You should be able to track these events.
One way to avoid this is, as you mentioned, calculate credit_used by a count query on all completed reservations.
I've got another problem on my SQL Tables but this time I've got more tables linked together.
What I realised and where I'm stuck:
I have tables about jobs, wages, employees.
I've done a query with these conditions:
The employee with the biggest wage in my company:
select employee_id, count(employee) as wage
from number_statistics
group by employee_id
having count(employee_id) in
(select max(count(employee_id)) from number_statistics group by employee_id);
This will show the ID of my employee with the biggest wage.
Where I'm stuck:
My next task is to create this query:
I need to display the employee with the biggest wage on three age categories:
Between 21-30; 30-45; 45-60;
The problem is that I don't have a field name AGE (and I'm not allowed to use one) in my tables.
I only have the birth date of my employees.
While I don't know the fully answer to this, I think your solution involves the function
TIMESTAMPDIFF(YEAR,birthdate,curdate()) BETWEEN 21 AND 30
This returns results that have between 21 and 30 years.
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.
Background:
We are setting up a promotions system to give away free products to registered customers. We're trying to design a database which is flexible enough to handle multiple products, and giveaways. The requirements are that products may be given away on a drip basis on a first come basis to qualified customers.
Example:
Apple wants to give away 1000 ipads in March.
They want to give away maximum of 1 per hour.
They want to give it to customers who are in California or New York.
They want to limit how many free ipads a customer can get (limit 1 per 15 days).
Data Structure:
Products - 1 entry per unique product. e.g. Apple iPad
ProductGiveAways
ProductID: AppleIpad
Quantity:1000
StartDate: 03/01/2014
End Date 03/31/2014
CustomerState: California,NewYork
PurchaseLimitDays: 15
Problem:
With the above structure we are able to do a query against our customers table and find out which are qualified for the promotion.
What I cannot figure out is the best way to:
Query customers in California or New York (is this a good use case for a join and another table?)
When a customer logs in to see what free items are not available to him, how can I exclude the Apple iPad if the customer has already gotten this freebie?
In other words:
Say amazon.com wants to show me DVDs which I have not already bought. What is the proper way to query that?
Is the right approach to first get a list of previously bought products and then Query with a NOT clause?
I'm assuming you'll have a table for what has been given away. In this table I would include a column for recipient id which can map back to the customer table. You can then create queries to find eligible recipients by searching for customers who have not met disqualifying conditions.
select customerid
from customer
where customerid not in (
select recipientid
from givenaway
where ..... and ....
)
Because there's not a definitive data structure defined, I'm going to use the following which you can tailor to whatever data structure you have designed yourself:
Product
ProductId - INTEGER (IDENTITY and PRIMARY KEY)
ProductName - VARCHAR
States
StateId - INTEGER (IDENTITY and PRIMARY KEY)
StateName - VARCHAR
Customer
CustomerId - INTEGER (IDENTITY and PRIMARY KEY)
StateId - INTEGER (FOREIGN KEY)
Promotion
PromotionId - INTEGER (IDENTITY and PRIMARY KEY)
ProductId - INTEGER (FOREIGN KEY)
Quantity - INTEGER
StartDate - DATETIME
End Date - DATETIME
PurchaseLimitDays - INTEGER
PromotionState
PromotionId - INTEGER (FOREIGN KEY)
StateId - INTEGER (FOREIGN KEY)
So in answer to your questions:
Query customers in California or New York (is this a good use case for a join and another table?)
Personally I would join to a centralized state table (PromotionState) in my above example, I'm sure there's a better way but you could do a condition such as:
WHERE
(SELECT COUNT * FROM PromotionState x WHERE x.PromotionId = p.PromotionId) = 0
OR NOT(ps.PromotionId IS NULL)
Alternatively you could do a GROUP BY and HAVING, using all the other columns as the items to GROUP BY and something like HAVING COUNT * = 0 OR HAVING SUM CASE WHEN (Conditions met) THEN 1 ELSE 0 END = 0
When a customer logs in to see what free items are not available to him, how can I exclude the Apple iPad if the customer has already gotten this freebie?
Say amazon.com wants to show me DVDs which I have not already bought. What is the proper way to query that?
As I've said you could use GROUP BY and HAVING to determine whether an item has been previously "won" by either using COUNT or SUM
Is the right approach to first get a list of previously bought products and then Query with a NOT clause?
There are probably better ways, sub queries can get very heavy and sluggish, I'd recommend trying some of the above techniques and then using a profiler to hopefully make it more efficient.
Some database design
First, when you set the CustomerState to California,NewYork you are violating the First Normal Form of database design.
So let's reorganize your domain model.
State - 1 Entry per unique state
...
Customer - 1 Entry per unique customer
StateId: (California|NewYork|...)
...
Product - 1 Entry per unique product
...
ProductGiveAways - Many entries per product
ProductID
Quantity
StartDate
End Date
PurchaseLimitDays
...
ProductGiveAways_State
ProductGiveAwaysId
StateId
...
Customer_Product - 1 Entry per bought product by customer
CustomerId
ProductId
PurchaseDate
...
Technical issues
When you want to query custoners in California or New York, all you have to do now is :
// This is just an example, you have to change the 'California', 'New York' with their ids
SELECT * FROM Customer WHERE StateId IN ('California', 'New York')
When a customer logs in to see what free items are available to him :
// It's not an accurate sql, just an example
SELECT Product.*
FROM Product
JOIN ProductGiveAways ON ProductId
JOIN ProductGiveAways_State ON ProductGiveAwaysId
WHERE ProductId NOT IN (
SELECT ProductId FROM Customer_Product JOIN ProductGiveAways ON ProductId
WHERE CustomerId = /* the customer id */
AND ( TO_DAYS(now()) - TO_DAYS(PurchaseDate) ) < PurchaseLimitDays
)
AND StateId = /* customer StateId */
AND StartDate < now() < End Date // Elligible ProductGiveAways
For Laravel We Use Something Like this, i hope you can relate to this query or you can use online laravel query converter for using it in mysql ( orator )
$user_id = auth()->user()->id;
Product::where('status', 'active')->whereNotIn('id', function($query) use ($user_id) { $query->select('product_id')->from(new OrderProduct->getTable())->where('user_id', $user_id)->where('status', 'delivered'); });