sql is unique code example

Example 1: DISTINCT SQL

SELECT DISTINCT column1, column1, ..... FROM TABLE
/*DISTINCT WILL NOT SELECT THE SAME VALUES IN SAME COLUMN*/

Example 2: set column as unique in sql server

ALTER TABLE Persons
ADD UNIQUE (ID);

Example 3: unique constraint mssql

USE AdventureWorks2012;  
GO  
CREATE TABLE Production.TransactionHistoryArchive4  
 (  
   TransactionID int NOT NULL,   
   CONSTRAINT AK_TransactionID UNIQUE(TransactionID)   
);   
GO

Example 4: sql unique

This constraint ensures all values in a column are unique.
Example 1 (MySQL): Adds a unique constraint to the id column when
creating a new users table.
CREATE TABLE users (
id int NOT NULL,
name varchar(255) NOT NULL,
UNIQUE (id)
);
Example 2 (MySQL): Alters an existing column to add a UNIQUE
constraint.
ALTER TABLE users
ADD UNIQUE (id);