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DBMS fungsional

Dunia basis data telah lama ditangkap oleh DBMS relasional yang menggunakan bahasa SQL. Sedemikian rupa sehingga spesies yang muncul disebut NoSQL. Mereka berhasil memenangkan tempat tertentu di pasar ini, tetapi DBMS relasional tidak akan mati, dan terus digunakan secara aktif untuk tujuan mereka.

Pada artikel ini saya ingin menjelaskan konsep basis data fungsional. Untuk pemahaman yang lebih baik, saya akan melakukan ini dengan membandingkan dengan model relasional klasik. Sebagai contoh, tugas dari berbagai tes SQL yang ditemukan di Internet akan digunakan.

Pendahuluan


Database relasional beroperasi pada tabel dan bidang. Dalam database fungsional, kelas dan fungsi akan digunakan sebagai gantinya. Bidang dalam tabel dengan tombol N akan ditampilkan sebagai fungsi parameter N. Alih-alih hubungan antar tabel, fungsi akan digunakan yang mengembalikan objek kelas yang sedang ditautkan. Alih-alih BERGABUNG komposisi fungsi akan digunakan.

Sebelum melanjutkan langsung ke tugas, saya akan menjelaskan tugas logika domain. Untuk DDL, saya akan menggunakan sintaks PostgreSQL. Untuk fungsional, sintaksnya sendiri.

Tabel dan Fields


Objek Sku sederhana dengan nama bidang dan harga:

Relasional

CREATE TABLE Sku
(
    id bigint NOT NULL,
    name character varying(100),
    price numeric(10,5),
    CONSTRAINT id_pkey PRIMARY KEY (id)
)


CLASS Sku;
name = DATA STRING[100] (Sku);
price = DATA NUMERIC[10,5] (Sku);

, Sku, .

, , , .

/ / . , . , :



CREATE TABLE prices
(
    skuId bigint NOT NULL,
    storeId bigint NOT NULL,
    supplierId bigint NOT NULL,
    dateTime timestamp without time zone,
    price numeric(10,5),
    CONSTRAINT prices_pkey PRIMARY KEY (skuId, storeId, supplierId)
)


CLASS Sku;
CLASS Store;
CLASS Supplier;
dateTime = DATA DATETIME (Sku, Store, Supplier);
price = DATA NUMERIC[10,5] (Sku, Store, Supplier);


, .



CREATE INDEX prices_date
    ON prices
    (skuId, storeId, supplierId, dateTime)


INDEX Sku sk, Store st, Supplier sp, dateTime(sk, st, sp);


, .

( ).

CLASS Department;
name = DATA STRING[100] (Department);

CLASS Employee;
department = DATA Department (Employee);
chief = DATA Employee (Employee);
name = DATA STRING[100] (Employee);
salary = DATA NUMERIC[14,2] (Employee);

1.1


, .



select a.*
from   employee a, employee b
where  b.id = a.chief_id
and    a.salary > b.salary


SELECT name(Employee a) WHERE salary(a) > salary(chief(a));

1.2


,



select a.*
from   employee a
where  a.salary = ( select max(salary) from employee b
                    where  b.department_id = a.department_id )


maxSalary ' ' (Department s) = 
    GROUP MAX salary(Employee e) IF department(e) = s;
SELECT name(Employee a) WHERE salary(a) = maxSalary(department(a));

//   ""
SELECT name(Employee a) WHERE 
    salary(a) = maxSalary(GROUP MAX salary(Employee e) IF department(e) = department(a));

. CREATE VIEW, . , .

1.3


ID , 3 .



select department_id
from   employee
group  by department_id
having count(*) <= 3


countEmployees ' ' (Department d) = 
    GROUP SUM 1 IF department(Employee e) = d;
SELECT Department d WHERE countEmployees(d) <= 3;

1.4


, , - .



select a.*
from   employee a
left   join employee b on (b.id = a.chief_id and b.department_id = a.department_id)
where  b.id is null


SELECT name(Employee a) WHERE NOT (department(chief(a)) = department(a));

1.5


ID .



with sum_salary as
  ( select department_id, sum(salary) salary
    from   employee
    group  by department_id )
select department_id
from   sum_salary a       
where  a.salary = ( select max(salary) from sum_salary )


salarySum ' ' (Department d) = 
    GROUP SUM salary(Employee e) IF department(e) = d;
maxSalarySum '  ' () = 
    GROUP MAX salarySum(Department d);
SELECT Department d WHERE salarySum(d) = maxSalarySum();


. , MS SQL.

2.1


1997 30 №1?

( ):
CLASS Employee '';
lastName '' = DATA STRING[100] (Employee);

CLASS Product '';
id = DATA INTEGER (Product);
name = DATA STRING[100] (Product);

CLASS Order '';
date = DATA DATE (Order);
employee = DATA Employee (Order);

CLASS Detail ' ';

order = DATA Order (Detail);
product = DATA Product (Detail);
quantity = DATA NUMERIC[10,5] (Detail);



select LastName
from Employees as e
where (
  select sum(od.Quantity)
  from [Order Details] as od
  where od.ProductID = 1 and od.OrderID in (
    select o.OrderID
    from Orders as o
    where year(o.OrderDate) = 1997 and e.EmployeeID = o.EmployeeID)
) > 30


sold (Employee e, INTEGER productId, INTEGER year) = 
    GROUP SUM quantity(OrderDetail d) IF 
        employee(order(d)) = e AND 
        id(product(d)) = productId AND 
        extractYear(date(order(d))) = year;
SELECT lastName(Employee e) WHERE sold(e, 1, 1997) > 30;

2.2


(, ) (), 1997- .

:
CLASS Customer '';
contactName '' = DATA STRING[100] (Customer);

customer = DATA Customer (Order);

unitPrice = DATA NUMERIC[14,2] (Detail);
discount = DATA NUMERIC[6,2] (Detail);



SELECT ContactName, ProductName FROM (
SELECT c.ContactName, p.ProductName
, ROW_NUMBER() OVER (
    PARTITION BY c.ContactName
    ORDER BY SUM(od.Quantity * od.UnitPrice * (1 - od.Discount)) DESC
) AS RatingByAmt
FROM Customers c
JOIN Orders o ON o.CustomerID = c.CustomerID
JOIN [Order Details] od ON od.OrderID = o.OrderID
JOIN Products p ON p.ProductID = od.ProductID
WHERE YEAR(o.OrderDate) = 1997
GROUP BY c.ContactName, p.ProductName
) t
WHERE RatingByAmt < 3


sum (Detail d) = quantity(d) * unitPrice(d) * (1 - discount(d));
bought '' (Customer c, Product p, INTEGER y) = 
    GROUP SUM sum(Detail d) IF 
        customer(order(d)) = c AND 
        product(d) = p AND 
        extractYear(date(order(d))) = y;
rating '' (Customer c, Product p, INTEGER y) = 
    PARTITION SUM 1 ORDER DESC bought(c, p, y), p BY c, y;
SELECT contactName(Customer c), name(Product p) WHERE rating(c, p, 1997) < 3;

PARTITION : , SUM ( 1), ( Customer Year, ), , ORDER ( bought, , ).

2.3


.

:
CLASS Supplier '';
companyName = DATA STRING[100] (Supplier);

supplier = DATA Supplier (Product);

unitsInStock '  ' = DATA NUMERIC[10,3] (Product);
reorderLevel ' ' = DATA NUMERIC[10,3] (Product);


select s.CompanyName, p.ProductName, sum(od.Quantity) + p.ReorderLevel — p.UnitsInStock as ToOrder
from Orders o
join [Order Details] od on o.OrderID = od.OrderID
join Products p on od.ProductID = p.ProductID
join Suppliers s on p.SupplierID = s.SupplierID
where o.ShippedDate is null
group by s.CompanyName, p.ProductName, p.UnitsInStock, p.ReorderLevel
having p.UnitsInStock < sum(od.Quantity) + p.ReorderLevel


orderedNotShipped ',   ' (Product p) = 
    GROUP SUM quantity(OrderDetail d) IF product(d) = p;
toOrder ' ' (Product p) = orderedNotShipped(p) + reorderLevel(p) - unitsInStock(p);
SELECT companyName(supplier(Product p)), name(p), toOrder(p) WHERE toOrder(p) > 0;


. . . :
CLASS Person;
likes = DATA BOOLEAN (Person, Person);
friends = DATA BOOLEAN (Person, Person);

. A, B, C , A B, B C, A C, A C.
:
SELECT Person a, Person b, Person c WHERE 
    likes(a, c) AND NOT friends(a, c) AND 
    friends(a, b) AND friends(b, c);

SQL. , , . . . . :
SELECT Person a, Person b, Person c WHERE 
    likes(a, c) AND NOT friends(a, c) AND 
    (friends(a, b) OR friends(b, a)) AND 
    (friends(b, c) OR friends(c, b));

UPD: dss_kalika:
SELECT 
   pl.PersonAID
  ,pf.PersonAID
  ,pff.PersonAID
FROM Persons                 AS p
--                      
JOIN PersonRelationShip      AS pl ON pl.PersonAID = p.PersonID
                                  AND pl.Relation  = 'Like'
--                     
JOIN PersonRelationShip      AS pf ON pf.PersonAID = p.PersonID 
                                  AND pf.Relation = 'Friend'
--               
JOIN PersonRelationShip      AS pff ON pff.PersonAID = pf.PersonBID
                                   AND pff.PersonBID = pl.PersonBID
                                   AND pff.Relation = 'Friend'
--           
LEFT JOIN PersonRelationShip AS pnf ON pnf.PersonAID = p.PersonID
                                   AND pnf.PersonBID = pff.PersonBID
                                   AND pnf.Relation = 'Friend'
WHERE pnf.PersonAID IS NULL 


;WITH PersonRelationShipCollapsed AS (
  SELECT pl.PersonAID
        ,pl.PersonBID
        ,pl.Relation 
  FROM #PersonRelationShip      AS pl 
  
  UNION 

  SELECT pl.PersonBID AS PersonAID
        ,pl.PersonAID AS PersonBID
        ,pl.Relation
  FROM #PersonRelationShip      AS pl 
)
SELECT 
   pl.PersonAID
  ,pf.PersonBID
  ,pff.PersonBID
FROM #Persons                      AS p
--                      
JOIN PersonRelationShipCollapsed  AS pl ON pl.PersonAID = p.PersonID
                                 AND pl.Relation  = 'Like'                                  
--                          
JOIN PersonRelationShipCollapsed  AS pf ON pf.PersonAID = p.PersonID 
                                 AND pf.Relation = 'Friend'
--                    
JOIN PersonRelationShipCollapsed  AS pff ON pff.PersonAID = pf.PersonBID
                                 AND pff.PersonBID = pl.PersonBID
                                 AND pff.Relation = 'Friend'
--                     
LEFT JOIN PersonRelationShipCollapsed AS pnf ON pnf.PersonAID = p.PersonID
                                   AND pnf.PersonBID = pff.PersonBID
                                   AND pnf.Relation = 'Friend'
WHERE pnf.[PersonAID] IS NULL



, — . SQL, , . , - , . — . C++, Python .

, :

  • . , . (, ), , , .
  • . (, sold, bought ..), . . , , sold , . , CREATE VIEW. , .
  • . ( ). , ( , — , ). , «» . , . , :
    CONSTRAINT sold(Employee e, 1, 2019) > 100 IF name(e) = '' MESSAGE  '-        2019 ';

  • . CLASS ClassP: Class1, Class2 . , .

, , Java, . , . , ( PostgreSQL) « ». , , . , , , .

Source: https://habr.com/ru/post/id458774/

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