How do I delete a reference constraint in SQL?

How do I delete a reference constraint in SQL?

The DROP CONSTRAINT command is used to delete a UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK constraint.

1. DROP a UNIQUE Constraint. To drop a UNIQUE constraint, use the following SQL:
2. DROP a PRIMARY KEY Constraint. To drop a PRIMARY KEY constraint, use the following SQL:
3. DROP a FOREIGN KEY Constraint.
4. DROP a CHECK Constraint.

How do I delete a foreign key constraint in SQL Server?

Creating a foreign key with DELETE and UPDATE CASCADE rules

1. Select the parent table and the primary key column in the parent table.
2. In the INSERT and UPDATE specifications, select Cascade for the delete rule.
3. Click on Close and save the table in the designer.

What is a reference constraint?

Referential constraint–Ensures that a value assigned to a column appears in a corresponding column in another table. Referential constraints are specified using the REFERENCES option. • Primary key constraint–Declares one or more columns for use in referential constraints in other tables. Primary keys must be unique.

Where does the DELETE statement conflict with the reference constraint?

The DELETE statement conflicted with the REFERENCE constraint ” FK_User_History_Tbl_Customer”. The conflict occurred in database ” KHUB_DB”, table ” dbo.User_History”, column ‘ UserId’. The statement has been terminated.

What does the error ” the DELETE statement conflicted with ” mean?

The error means that you have data in other tables that references the data you are trying to delete. You would need to either drop and recreate the constraints or delete the data that the Foreign Key references.

Do you remove references from a TRUNCATE statement?

To TRUNCATE you must remove the references. TRUNCATE is a DDL statement (comparable to CREATE and DROP) not a DML statement (like INSERT and DELETE) and doesn’t cause triggers, whether explicit or those associated with references and other constraints, to be fired.

Why is Cascade delete conflicted with the DELETE statement?

The situation described by the OP is where they are trying to delete the child row before deleting the rows that depend on it OR before removing the data from the FK column. Sure, cascade delete would mean only a single step if they deleted the row in the parent table, but it doesn’t solve this problem. The accepted answers obviously do though.

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