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What is drop constraint?

What is drop constraint?

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

How do I drop a constraint in a table?

The SQL syntax to remove a constraint from a table is,

  2. ALTER TABLE Customer DROP INDEX Con_First;

How do I drop a constraint in SQL?

Using SQL Server Management Studio

  1. In Object Explorer, expand the table with the check constraint.
  2. Expand Constraints.
  3. Right-click the constraint and click Delete.
  4. In the Delete Object dialog box, click OK.

How do I view constraints in SQL?

The syntax for enabling a check constraint in SQL Server (Transact-SQL) is: ALTER TABLE table_name WITH CHECK CHECK CONSTRAINT constraint_name; table_name.

How do you drop multiple constraints?

To drop an existing constraint, specify the DROP CONSTRAINT keywords and the identifier of the constraint. To drop multiple constraints on the same table, the constraint names must be in comma-separated list that is delimited by parentheses. The constraint that you drop can have an ENABLED, DISABLED, or FILTERING mode.

Can we drop primary key constraint?

You cannot drop a primary key constraint if another table has a foreign key constraint that references the primary key. To drop the primary key, you must first drop all foreign keys that reference it.

What happens if a primary key is deleted?

When the primary key is deleted, the corresponding index is deleted.

Can we delete primary key without deleting foreign key?

If you want the department to remain and to be able to do this, you will need to alter the foreign key to include ON DELETE SET NULL. Otherwise, you will have to drop the constraint, perform the delete, and recreate the constraint. @ypercube : If you set foreign_key_checks to 0 then you can.

How do you find constraints?

You have to query the data dictionary, specially the USER_CONS_COLUMNS view to see the table columns and the corresponding constraints like this:

  1. SELECT * FROM user_cons_columns.
  2. SELECT * FROM user_constraints.
  3. all_cons_columns.
  4. all_constraints.
  5. AND owner = ”

What are the key constraints?

A primary key constraint is a column or combination of columns that has the same properties as a unique constraint. You can use a primary key and foreign key constraints to define relationships between tables.