Mastering SQL Server Composite Primary Keys for Efficient Data Management

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A composite primary key is a primary key that consists of two or more columns. It is used to uniquely identify a row in a table, and it can be created by specifying multiple columns as the primary key when creating a table or by altering an existing table.

To master SQL Server composite primary keys, follow these steps:

  1. Understand the concept of primary keys: A primary key is a unique identifier for a row in a table. It must be unique and not null. When creating a table, you can specify one or more columns as the primary key.
  2. Determine the columns for the composite primary key: When creating a composite primary key, you need to determine which columns will be included in the key. The columns you choose should be unique and not null.
  3. Create the table with the composite primary key: When creating a table with a composite primary key, you can specify the columns that will make up the key in the CREATE TABLE statement. For example:CREATE TABLE MyTable ( Column1 INT, Column2 VARCHAR(50), Column3 DATE, CONSTRAINT PK_MyTable PRIMARY KEY (Column1, Column2, Column3) );
  4. Alter an existing table to add a composite primary key: If you need to add a composite primary key to an existing table, you can use the ALTER TABLE statement. For example:ALTER TABLE MyTable ADD CONSTRAINT PK_MyTable PRIMARY KEY (Column1, Column2, Column3);
  5. Use the composite primary key in queries: Once you have created the composite primary key, you can use it in queries to uniquely identify rows in the table. For example:SELECT * FROM MyTable WHERE Column1 = 1 AND Column2 = ‘Value’ AND Column3 = ‘2023-04-09’;

By mastering SQL Server composite primary keys, you can ensure the uniqueness and integrity of your data and improve the performance of your queries.

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