SQL Server 2019

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CREATE tABLE SHAREOUTWARDZ (ShareoutwardzID int PRIMARY KEY)
CREATE TABLE [USER]
(
    UserID int IDENTITY(1, 1) PRIMARY KEY,
    URL varchar(50) NOT NULL,
    Name varchar(20) NOT NULL,
    Password varchar(50) NOT NULL,
    Email varchar(100) NOT NULL,
    Age int NOT NULL,
    Gender char(1) NOT NULL,
    Location varchar(50) NOT NULL,
    Description varchar(200) NULL,
    NbFollower int NULL DEFAULT 0,
    Rating int NULL DEFAULT 0
);
ALTER TABLE [USER]
    ADD ShareoutwardzID int FOREIGN KEY REFERENCES SHAREOUTWARDZ(ShareoutwardzID),
    CONSTRAINT Age CHECK (Age>=18);
INSERT INTO [USER](Name, URL, Password, Email, Age, Gender, Location, Description, Rating)
VALUES
('lily', '/NAME', 'azertyuop123', 'lily@hotmail.com', 21, 'F', 'USA', NULL, 4),
('MArk', '/NAME', 'azertyuop123', 'mark@hotmail.com', 21, 'M', 'USA', NULL, 4),
('Mary', '/NAME', 'azertyuop123', 'Mary@hotmail.com', 21, 'F', 'USA', NULL, 4),
('David', '/NAME', 'azertyuop123', 'david@hotmail.com', 21, 'M', 'USA', NULL, 4)
;
4 rows affected

CREATE TABLE FOLLOWER(UserID int PRIMARY KEY);
INSERT FOLLOWER VALUES (9)
1 rows affected

CREATE TABLE FOLLOWING_USER
(
    [User] int NOT NULL FOREIGN KEY REFERENCES [USER](UserID),
    Follower int NOT NULL FOREIGN KEY REFERENCES FOLLOWER(UserID),
);
INSERT INTO FOLLOWING_USER([User], Follower)
VALUES
(1, 9),
(2, 9),
(2, 9),
(3, 9);
4 rows affected

    UPDATE [USER]
SET NbFollower = (SELECT count(*)
                  FROM FOLLOWING_USER FU
                  
                  WHERE FU.[User] = [USER].UserID)
4 rows affected

SELECT * FROM [USER]


UserID
URL
Name
Password
Email
Age
Gender
Location
Description
NbFollower
Rating
ShareoutwardzID


1
/NAME
lily
azertyuop123
lily@hotmail.com
21
F
USA
null
1
4
null

2
/NAME
MArk
azertyuop123
mark@hotmail.com
21
M
USA
null
2
4
null

3
/NAME
Mary
azertyuop123
Mary@hotmail.com
21
F
USA
null
1
4
null

4
/NAME
David
azertyuop123
david@hotmail.com
21
M
USA
null
0
4
null

UserID	URL	Name	Password	Email	Age	Gender	Location	Description	NbFollower	Rating	ShareoutwardzID
1	/NAME	lily	azertyuop123	lily@hotmail.com	21	F	USA	null	1	4	null
2	/NAME	MArk	azertyuop123	mark@hotmail.com	21	M	USA	null	2	4	null
3	/NAME	Mary	azertyuop123	Mary@hotmail.com	21	F	USA	null	1	4	null
4	/NAME	David	azertyuop123	david@hotmail.com	21	M	USA	null	0	4	null