How to Create a Composite Primary Key in SQL Server 2008?

Creating Composite Primary Keys in SQL Server 2008

A composite primary key is a unique combination of two or more columns that identifies each row of a table. This ensures that each row in the table is distinct. Creating a composite primary key in SQL Server 2008 is a straightforward process.

To create a composite primary key, follow these steps:

1. Declare the columns that you want to include in the primary key as NOT NULL to enforce uniqueness. For example:

column_a integer not null,
column_b integer not null,

2. Use the PRIMARY KEY constraint with the ( and ) symbols to specify the columns that comprise the primary key. For instance:

primary key (column_a, column_b)

This creates a primary key consisting of the column_a and column_b columns. Each combination of values in these columns must be unique for each row in the table.

Example:

Let's create a table named my_table with a composite primary key consisting of the column_a and column_b columns:

create table my_table (
     column_a integer not null,
     column_b integer not null,
     column_c varchar(50),
     primary key (column_a, column_b)
);

Now, each row in the my_table table will be uniquely identified by the combination of column_a and column_b.

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