Insert statement error - sql

Question

I have table dbo.Students_Old with columns :
Name(varchar), DocNum(int), Group(varchar), Form(varchar).
It have no primary key and I need to normalize this table. So I am going to make three tables:
dbo.Students(StudentId(int primary key), Name(varchar), Group(int fk),
Form(int fk),
dbo.Forms(FormId(int pk), FName(varchar)), dbo.Groups(GroupId(int pk),
GName(varchar)).
And also I need to fill all this tables with data from dbo.Students_Old. My code is:
CREATE TABLE dbo.Groups(GroupId int IDENTITY(1,1) PRIMARY KEY, GName nvarchar(10));
GO
INSERT INTO dbo.Groups(GName)
select Group
from dbo.Students_Old
group by Group
GO
CREATE TABLE dbo.Forms(FormId int IDENTITY(1,1) PRIMARY KEY, Form nvarchar(20));
INSERT INTO dbo.Forms(Form)
select Form
from dbo.Students_Old
group by Form
GO
CREATE TABLE dbo.Students (StudentId int PRIMARY KEY, Name nvarchar(50),
Form int NOT NULL,
Group int NOT NULL,
CONSTRAINT Form FOREIGN KEY(StudentId) REFERENCES dbo.Forms(FormId),
CONSTRAINT Grup FOREIGN KEY(StudentId) REFERENCES dbo.Groups(GroupId));
GO
INSERT INTO dbo.Students(StudentId, Name, Form, Group)
select DocNum, Name, f.FormId, g.GroupId
from dbo.Students_Old s
join dbo.Forms f on s.Form=f.Form
join dbo.Groups g on s.Group=g.GName
Also Students_Old.DocNum is unique.
Tables creates normaly, but on the insert statement i have an error:
The INSERT statement conflicted with the FOREIGN KEY constraint "Form". The conflict occurred in database "DBNames", table "dbo.Forms", column 'FormId'.
Help me please.

Answer 1

Execute the below query on a new database
CREATE TABLE dbo.Groups(GroupId int IDENTITY(1,1) PRIMARY KEY, GName nvarchar(10));
GO
INSERT INTO dbo.Groups(GName)
select Group
from dbo.Students_Old
group by Group
GO
CREATE TABLE dbo.Forms(FormId int IDENTITY(1,1) PRIMARY KEY, Form nvarchar(20));
INSERT INTO dbo.Forms(Form)
select Form
from dbo.Students_Old
group by Form
GO
CREATE TABLE dbo.Students (StudentId int PRIMARY KEY, Name nvarchar(50),
Form int NOT NULL,
[Group] int NOT NULL,
CONSTRAINT Form FOREIGN KEY(Form) REFERENCES dbo.Forms(FormId),
CONSTRAINT Grup FOREIGN KEY(Group) REFERENCES dbo.Groups(GroupId));
GO
INSERT INTO dbo.Students(StudentId, Name, Form, Group)
select DocNum, Name, f.FormId, g.GroupId
from dbo.Students_Old s
join dbo.Forms f on s.Form=f.Form
join dbo.Groups g on s.Group=g.GName
I've changed to following lines
CONSTRAINT Form FOREIGN KEY(Form) REFERENCES dbo.Forms(FormId),
CONSTRAINT Grup FOREIGN KEY([Group]) REFERENCES dbo.Groups(GroupId));
In your code the foreign key is made on StudentID column

Answer 2

Not sure if that is the case, since you get the FOREIGN KEY error, but try avoiding column names like GROUP or other reserved words. While you can avoid errors on table creation step, you can face serious problems during modifications/updates on such tables.

Answer 3

execute below query.
CREATE TABLE dbo.Groups(GroupId int IDENTITY(1,1) PRIMARY KEY, GName nvarchar(10));
GO
INSERT INTO dbo.Groups(GName)
select [Group]
from dbo.Students_Old
group by [Group]
GO
CREATE TABLE dbo.Forms(FormId int IDENTITY(1,1) PRIMARY KEY, Form nvarchar(20));
INSERT INTO dbo.Forms(Form)
select Form
from dbo.Students_Old
group by Form
GO
CREATE TABLE dbo.Students (StudentId int PRIMARY KEY, Name nvarchar(50),
Form int NOT NULL,
[Group] int NOT NULL,
CONSTRAINT Form FOREIGN KEY(StudentId) REFERENCES dbo.Forms(FormId),
CONSTRAINT Grup FOREIGN KEY(StudentId) REFERENCES dbo.Groups(GroupId));
GO
INSERT INTO dbo.Students(StudentId, Name, Form, [Group])
select DocNum, Name, f.FormId, g.GroupId
from dbo.Students_Old s
join dbo.Forms f on s.Form=f.Form
join dbo.Groups g on s.[Group]=g.GName