Unable to set foreign key for my computed column - sql

Question

I can't set the foreign key for my advertisement table or should I say how do I add datatype for my computed column in employer table ? error details below
CREATE Table Employer
(
No Int NOT NULL IDENTITY(1,1),
EmployerID AS 'EID'+ CAST(No as VARCHAR(50)) PERSISTED NOT NULL ,
CONSTRAINT PK_Employer PRIMARY KEY CLUSTERED(EmployerID),
EUsername CHAR(20) NOT NULL,
EPassword CHAR(20) NOT NULL,
Name VARCHAR(20) NOT NULL,
Contact_Number INT NOT NULL,
Email CHAR(20) NOT NULL,
Company_Name CHAR(30) NOT NULL,
Current_Position VARCHAR(30) NULL
);
CREATE Table Advertisement
(
No Int NOT NULL IDENTITY(1,1),
AdvertisementID AS 'AID'+ CAST(No as VARCHAR(10)) PERSISTED ,
CONSTRAINT PK_Advertisement PRIMARY KEY CLUSTERED(AdvertisementID) ,
Employer_ID VARCHAR(10) Foreign Key References Employer(EmployerID) NOT NULL,
Company_Name VARCHAR(30) NOT NULL,
Company_Location CHAR(30) NULL,
Job_Position VARCHAR(30)NOT NULL,
Job_Description VARCHAR(100) NULL,
Skills_Requirement VARCHAR(100) NULL,
Education_Requirement CHAR(50) NOT NULL,
Salary CHAR(20) NOT NULL
);
This is the error I keep getting :
Msg 1753, Level 16, State 0, Line 27
Column 'Employer.EmployerID' is not the same length or scale as referencing column 'Advertisement.EmployerID' in foreign key 'FK__Advertise__Emplo__07C12930'. Columns participating in a foreign key relationship must be defined with the same length and scale.
Msg 1750, Level 16, State 0, Line 27
Could not create constraint or index. See previous errors.

Answer 1

note that the foreign key relationship must be defined with the same length and scale for both foreign key and primary key
so you must set EmployerID field to varchar(50) in advertisement table
Its recommended to use BIGINT auto increment field type for EmployerID.
and use Employer table's EmployerID field as you foreign key.
CREATE TABLE [Employer](
[EmployerID] [bigint] IDENTITY(1,1) NOT NULL,
[EUsername] [char](20) NOT NULL,
[EPassword] [char](20) NOT NULL,
[Name] [varchar](20) NOT NULL,
[Contact_Number] [int] NOT NULL,
[Email] [char](20) NOT NULL,
[Company_Name] [char](30) NOT NULL,
[Current_Position] [varchar](30) NULL,
CONSTRAINT [PK_Employer] PRIMARY KEY CLUSTERED
(
[EmployerID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
CREATE TABLE [Advertisement](
[AdvertisementID] [bigint] IDENTITY(1,1) NOT NULL,
[fk_Employer_ID] [bigint] NOT NULL,
[Company_Name] [varchar](30) NOT NULL,
[Company_Location] [char](30) NULL,
[Job_Position] [varchar](30) NOT NULL,
[Job_Description] [varchar](100) NULL,
[Skills_Requirement] [varchar](100) NULL,
[Education_Requirement] [char](50) NOT NULL,
[Salary] [char](20) NOT NULL,
CONSTRAINT [PK_Advertisement] PRIMARY KEY CLUSTERED
(
[AdvertisementID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
ALTER TABLE [Advertisement] WITH CHECK ADD CONSTRAINT [FK_Advertisement_Employer] FOREIGN KEY([fk_Employer_ID])
REFERENCES [Employer] ([EmployerID])
ALTER TABLE [Advertisement] CHECK CONSTRAINT [FK_Advertisement_Employer]