How to Alter a Foreign Key-Referenced Integer Column to Double Precision in EF Databases?

Foreign Key Dependency Issue: Altering 'Rating' Column from int to double

This issue arises when an EF database table has a column (e.g., 'Rating') that is an int and is referenced by a foreign key in another table. Changing the data type of 'Rating' from int to double can trigger an error:

The object 'DF__*'' is dependent on column '*''. ALTER TABLE ALTER COLUMN * failed because one or more objects access this column.

Cause:

When the 'Rating' column was originally defined as int, the DBMS (e.g., SQL Server) automatically created a foreign key constraint referencing it. This constraint enforces the integrity of the database by ensuring that any value in the 'Rating' column corresponds to a valid row in the referenced table.

Solution:

To successfully change 'Rating' from int to double, the foreign key constraint must be removed first.

1. Identify the Constraint:

   In Object Explorer, expand the table attributes and navigate to the Constraints category. Locate the constraint associated with the 'Rating' column, such as 'DF_Movies_Rating__48CFD27E'.

2. Remove the Constraint:

   Right-click on the constraint and select Remove. This will drop the constraint from the database.

3. Alter the Column:

   After removing the constraint, you can now alter the 'Rating' column to data type double using the appropriate SQL statement.

4. Recreate the Constraint:

   Once the 'Rating' column has been altered, you can recreate the foreign key constraint to maintain database integrity.

By following these steps, you can successfully change the data type of the 'Rating' column without encountering the dependency error.

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