Unique Vs. Primary Key - Referential Integrity - Have you tried...?

When we create a Referential integrity, Parent column can be a PRIMARY KEY or UNIQUE column!
 
OK.
1. Crete a Parent Table
CREATE TABLE MasterTable1
(
Id    INT IDENTITY(1,1) PRIMARY KEY,
Column1 VARCHAR(10)
)
GO

2. Create a Child table & Refer MasterTable1
CREATE TABLE ChildTable1
(
Id    INT IDENTITY(1,1) PRIMARY KEY,
MasterID INT FOREIGN KEY REFERENCES MasterTable1,
Column2 VARCHAR(10)
)
GO

So, The above statement uses only the Parent Table name. But, not Primary Key column.

By default, It refers the PRIMARY KEY column of the reference table(MasterTable1). So, no need to give the PRIMARY KEY column name explicitly.

But, Have you tried with UNIQUE key for the same scenario ?

1. Crete a Parent Table
CREATE TABLE MasterTable1
(
Id    INT IDENTITY(1,1) UNIQUE,
Column1 VARCHAR(10)
)
GO

2. Create a Child table & Refer MasterTable1
CREATE TABLE ChildTable1
(
Id    INT IDENTITY(1,1) PRIMARY KEY,
MasterID INT FOREIGN KEY REFERENCES MasterTable1,
Column2 VARCHAR(10)
)
GO

You will get an Err message!

Msg 1773, Level 16, State 0, Line 1
Foreign key 'FK__ChildTabl__Maste__658C0CBD' has implicit reference to object 'MasterTable1' which does not have a primary key defined on it.
Msg 1750, Level 16, State 0, Line 1
Could not create constraint. See previous errors.

So, when referring an UNIQUE column, It should be TableName(ColumnName)

CREATE TABLE ChildTable1
(
Id    INT IDENTITY(1,1) PRIMARY KEY,
MasterID INT FOREIGN KEY REFERENCES MasterTable1(Id),
Column2 VARCHAR(10)
)
GO

So, Using TableName(columnName) is mandatory when referring an UNIQUE key column!!!

Table level constraint does not specify column list, table 'TableName'.

When creating Primary Key or Foreign Key like constraint, The following error occurred..

Table level constraint does not specify column list, table 'TableName'.

Meaning:
Column Name or Column List not specified for the constraints.

When creating Table:
IF OBJECT_ID('Tb_Table1','U') IS NULL
CREATE TABLE Tb_Table1
(
Id INT IDENTITY(1,1),
Column1 VARCHAR(10),
CONSTRAINT PK_Id PRIMARY KEY
)

or

When adding constraint on existing table:
ALTER TABLE Tb_Table1 ADD CONSTRAINT PK_Id PRIMARY KEY
GO

The error occurred, Here No column or Column list specified..

The script should be as follows...

IF OBJECT_ID('Tb_Table1','U') IS NULL
CREATE TABLE Tb_Table1
(
Id INT IDENTITY(1,1),
Column1 VARCHAR(10),
CONSTRAINT PK_Id PRIMARY KEY(Id)
)

or

ALTER TABLE Tb_Table1 ADD CONSTRAINT PK_Id PRIMARY KEY (Id)
GO