how to make a column unique in SQL
ALTER TABLE Persons
ADD CONSTRAINT UC_Person UNIQUE (ID,LastName);how to make a column unique in SQL
ALTER TABLE Persons
ADD CONSTRAINT UC_Person UNIQUE (ID,LastName);unique constraint mssql
USE AdventureWorks2012;
GO
CREATE TABLE Production.TransactionHistoryArchive4
(
TransactionID int NOT NULL,
CONSTRAINT AK_TransactionID UNIQUE(TransactionID)
);
GOunique element in sql
DISTINCT
- select distinct * from employees; ==> retrieves any row if it has at
least a single unique column.
- select distinct first_name from employees; ==> retrieves unique names
from table. (removes duplicates)
- select distinct count(*) from employees; retrieve number of unique rows
if any row has at least a single unique data.Copyright © 2021 Codeinu
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