unique constraint menas code example
Example 1: how to drop a unique constraint in sql
SHOW CREATE TABLE [tableName]
-- Find the constraintID after CONSTRAINT 'constraintID'
ALTER TABLE [tableName] DROP FOREIGN KEY constraintID
Example 2: unique constraint mssql
USE AdventureWorks2012;
GO
CREATE TABLE Production.TransactionHistoryArchive4
(
TransactionID int NOT NULL,
CONSTRAINT AK_TransactionID UNIQUE(TransactionID)
);
GO