unique constraint postgres code example

Example 1: unique constraint mssql

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

Example 2: postgresql resolv duplicate value violates unique constraint

SELECT setval(pg_get_serial_sequence('users', 'id'), coalesce(max(id)+1, 1), false) FROM users;