CREATE TABLE Users(
    UserID INT PRIMARY KEY,
    UserName VARCHAR(20),
    Password VARCHAR(20),
    CustomerID INT UNIQUE,
    CONSTRAINT FK_Users_Customers
    FOREIGN KEY (CustomerID)
    REFERENCES Customers(CustomerID)
)

CREATE TABLE Payments(
    PaymentID INT PRIMARY KEY,
    DATE DATE,
    Amount DECIMAL(10, 2),
    LoanID INT,
    CONSTRAINT FK_Payments_Loans
    FOREIGN KEY (LoanID)
    REFERENCES Loans(LoanID)
)

CREATE TABLE CreditHistory(
    CreditHistoryID INT PRIMARY KEY,
    Mark VARCHAR(1),
    StartDate DATE,
    EndDate DATE,
    CustomerID INT,
    CONSTRAINT FK_CreditHistory_Customers
    FOREIGN KEY (CustomerID)
    REFERENCES Customers(CustomerID)
)

ALTER TABLE
    Employees
ADD ManagerID INT
ALTER TABLE Employees
ADD FOREIGN KEY(ManagerID)
REFERENCES Employees(EmployeeID)