Insert Into, Conflit with Foreign Key - sql

Question

create table Interventions
(
InterventionID BIGINT IDENTITY (1,1) PRIMARY KEY NOT NULL,
InterventionCustomerID BIGINT FOREIGN KEY REFERENCES Customer(CustomerID) NOT NULL,
InterventionMalfunctionDescription NVARCHAR(MAX) NOT NULL,
CustomerID BIGINT FOREIGN KEY REFERENCES Customer(CustomerID),
EmployeeID INT FOREIGN KEY REFERENCES Employees(EmployeeID),
TypeOfEquipementID INT FOREIGN KEY REFERENCES TypeOfEquipements(TypeOfEquipementID),
StatusID INT FOREIGN KEY REFERENCES TypeOfStatus(StatusID),
SerialNumber VARCHAR(255) FOREIGN KEY REFERENCES SerialNumbers(SerialNumber),
GroupID INT FOREIGN KEY REFERENCES TypeOfGroup(GroupID) NOT NULL,
InterventionCreateDate DATETIME NOT NULL,
InterventionStartDate DATETIME,
InterventionFinnishDate DATETIME,
InterventionArchiveDate DATETIME
);
create table Customer
(
CustomerID BIGINT IDENTITY(1,1) PRIMARY KEY NOT NULL,
OrganizationName VARCHAR(255) NOT NULL,
Telephone VARCHAR(255),
MobileTelephone VARCHAR(255) NOT NULL,
CustomerAdressLine1 VARCHAR(255) NOT NULL,
CustomerAdressLine2 VARCHAR(255),
PostalCode VARCHAR(255) NOT NULL,
FederalTaxID VARCHAR(255) UNIQUE NOT NULL,
EmailAddress VARCHAR(255) UNIQUE NOT NULL,
SageCustomerID BIGINT UNIQUE
);
INSERT INTO Interventions(InterventionCustomerID, InterventionMalfunctionDescription, CustomerID, EmployeeID, TypeOfEquipementID, StatusID, SerialNumber, GroupID, InterventionCreateDate, InterventionStartDate, InterventionFinnishDate, InterventionArchiveDate) VALUES
('1', 'abc', '4', '4', '1', '1', 'SerialNumber1', '1', '2019-01-01', '2019-01-02', '2019-01-03', '2019-01-04'),
('2', 'abc', '5', '5', '2', '2', 'SerialNumber2', '2', '2019-02-01', '2019-02-02', '2019-02-03', '2019-02-03'),
('3', 'abc', '6', '6', '3', '3', 'SerialNumber3', '3', '2019-03-01', '2019-03-02', '2019-03-03', '2019-03-04');
Select * from Customer;
Erro:
The INSERT statement conflicted with the FOREIGN KEY constraint "FK__Intervent__Inter__6C190EBB". The conflict occurred in database "ADSGLOBAL", table "dbo.Customer", column 'CustomerID'.

Answer 1

You have a constraint on InterventionCustomerID that says it references Customer(CustomerID).
Your insert statement says you're trying to insert the values 1, 2, 3 in to that column.
Your SELECT * FROM customer shows that customers 1, 2, 3 don't exist in that table.
You can't insert records for customers 1, 2, 3 until you've created them in the Customer table.