The UNIQUE constraint ensures that all values in a column are different. Both the UNIQUE and PRIMARY KEY constraints provide a guarantee for uniqueness for a column or set of columns.

6 days ago · You can create a unique constraint in SQL Server by using SQL Server Management Studio or Transact-SQL to ensure no duplicate values are entered in specific columns that don't …

In this tutorial, you will learn how to use the SQL UNIQUE constraint to ensure all values in a column or set of columns are distinct.

Sep 8, 2025 · The UNIQUE constraint in SQL ensures that values in a column or set of columns are distinct, preventing duplicates. Unlike a PRIMARY KEY, it allows multiple NULL values since each …

SQL unique constraint is a type of constraint that ensures that the data in a column or set of columns is unique across all rows in a table. It is used to prevent duplicate values from being inserted into a …

A unique constraint in SQL is a rule that ensures all values in a column (or combination of columns) are distinct across rows in a table. Unlike a primary key, which also enforces uniqueness, a unique …

Sep 13, 2024 · A UNIQUE constraint is a rule that we can apply to one or more columns in a database table to ensure that the values in those columns are unique across all rows.

Both Unique constraint and Primary key constraint enforce uniqueness. It is recommended to use Unique constraint instead of Primary key constraint whenever you want to enforce uniqueness in a …

Mar 3, 2024 · When adding unique constraints to a SQL database, it’s crucial to remember that not all database systems handle them in the same way. I’ve navigated the syntax and peculiarities of …

Feb 4, 2021 · By using a UNIQUE constraint on a particular column, we ensure that this column cannot contain two of the same values. Let’s see an example using the Person table with the columns …