Why Does My SQL Server INSERT Statement Fail with 'Cannot Insert NULL into Column 'id''?

SQL Server INSERT Statement Failure: NULL Value in Non-Nullable Column 'id'

The SQL statement:

<code class="language-sql">INSERT INTO role (name, created) VALUES ('Content Coordinator', GETDATE()), ('Content Viewer', GETDATE())</code>

results in the error:

<code>Msg 515, Level 16, State 2, Line 1
Cannot insert the value NULL into column 'id', table 'CMT_DEV.dbo.role'; column does not allow nulls. INSERT fails.
The statement has been terminated.</code>

This error arises because the id column is defined as NOT NULL, yet the INSERT statement doesn't specify a value for it. SQL Server defaults to NULL if a value isn't provided for a column, leading to the constraint violation.

Here's how to fix this:

• Explicitly Set id: Provide a value for the id column in your INSERT statement. This is only practical if you have a way to determine the next available ID (e.g., you're manually managing IDs).

• Use an Auto-Incrementing Column: The best solution is to make the id column an auto-incrementing column. This automatically generates unique IDs for each new row. In SQL Server Management Studio (SSMS):

  1. Open the table in Design mode.
  2. Select the id column.
  3. In the Column Properties, find "Identity Specification."
  4. Set Is Identity to Yes and Identity Increment to 1. (You can adjust Identity Increment if needed.)

After implementing the auto-increment, your INSERT statement will work correctly without needing to specify the id value. The database will handle ID generation automatically.

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