Detailed tutorial on how to use SQL Server to automatically generate serial numbers

Using the IDENTITY attribute in SQL Server, you can automatically generate sequence numbers in the table, starting from the specified starting value, incrementing the specified increment each time a new row is inserted.

How to use SQL Server to automatically generate serial numbers

Generating a sequence number in SQL Server is a way to assign unique numeric values ​​to each row in a table. Serial number fields are often used to identify rows in tables and help enforce data integrity.

Step 1: Create a table

First, you need to create a table to add the sequence number. The following example creates a table named "Customers":

 <code class="sql">CREATE TABLE Customers ( CustomerID INT IDENTITY(1, 1), FirstName VARCHAR(50), LastName VARCHAR(50) );</code>

Step 2: Use the IDENTITY attribute

The "IDENTITY" attribute is used to automatically generate sequence numbers in the table. In the definition of the "CustomerID" column, we specify:

• IDENTITY(1, 1) : means that starting from 1, the value of the column will increase by 1 each time a new row is inserted.

Step 3: Insert the data

You can now insert data into the "Customers" table using the following query:

 <code class="sql">INSERT INTO Customers (FirstName, LastName) VALUES ('John', 'Doe');</code>

result:

After the insert query is executed, the "CustomerID" field will automatically generate a unique serial number value. For the above query, the value of "CustomerID" will be 1.

Other options:

• IDENTITY(start, increment) : Specifies the starting value and increment of the sequence number. For example, "IDENTITY(10, 5)" will start at 10, incrementing by 5 each time.
• NOT NULL : Ensure that the "CustomerID" field does not allow null values.
• PRIMARY KEY : Set "CustomerID" as the primary key to ensure that each row in the table has a unique order number.

advantage:

• Automation: Serial numbers are automatically generated without manual allocation.
• Uniqueness: Each sequence number is unique, helping to identify and distinguish rows in the table.
• Performance: Using the IDENTITY attribute is more efficient than generating sequence numbers using triggers or user-defined functions.

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