Quick Answer: Can We Delete A Table With Foreign Key?

How do you delete a table that has a foreign key reference?

To delete a foreign key constraintIn Object Explorer, expand the table with the constraint and then expand Keys.Right-click the constraint and then click Delete.In the Delete Object dialog box, click OK.Jul 25, 2017.

Can we drop a table with foreign key?

In SQL Server, you cannot drop a table if it is referenced by a FOREIGN KEY constraint. You have to either drop the child tables before removing the parent table, or remove foreign key constraints.

Which clause is used to remove a foreign key constraint?

DROP’ clauseTo remove a foreign key constraint, the ‘DROP’ clause is used.

How do you truncate a table with foreign key constraints?

You can’t truncate a table that has a foreign key constraint, that is the whole reason for having a constraint. You will need to delete and re-create the constraints so make sure you script them out before deleting them.

Can a foreign key be updated?

No the foreign key is not updated automatically. You need to update the foreign key in the tables in which it is referenced by yourself else it would result in referential integrity exception. For updating the foreign key automatically you may use TRIGGERS.

How do I change a foreign key to a primary key?

Open table in design mode.Click Relationship button from top toolbar.Select the required FK relations (one by one)Right Side – Expand INSERT or UPDATE Specification.Change the UPDATE Rule to – Cascade.Sep 4, 2009

How do you assign a foreign key?

Creating a Foreign key constraintCreate a foreign key while creating a table. … Create a foreign key after creating a table. … Create a foreign key without checking for an existing data. … Create a foreign key with DELETE/UPDATE rules. … Disable constraint. … Enable constraint. … Enable constraint with checking existing data.Apr 5, 2019

What is drop table if exists?

The DROP TABLE statement deletes the specified table, and any data associated with it, from the database. The IF EXISTS clause allows the statement to succeed even if the specified tables does not exist. … Attempting to drop the table before dropping the procedure will result in an error.

Can we delete primary key?

We can remove PRIMARY KEY constraint from a column of an existing table by using DROP keyword along with ALTER TABLE statement.

Does a foreign key have to be a primary key?

A foreign key must refer to an entire primary key, and not just part of it. Consider a Department table with a primary key of company_name + department_name. An Employee table should only refer to both attributes and not to department_name alone. Lack of foreign key indexes.

Which method is used to remove a table?

The drop table command is used to delete a table and all rows in the table. To delete an entire table including all of its rows, issue the drop table command followed by the tablename.

Does drop table need commit?

Data definition language (DDL) statements that define or modify database objects. … CREATE TABLE and DROP TABLE statements do not commit a transaction if the TEMPORARY keyword is used. (This does not apply to other operations on temporary tables such as ALTER TABLE and CREATE INDEX , which do cause a commit.)

How do you force delete a table in SQL?

Sql query to forcefully drop a table even if foreign key constraint on table in sql server–Change the table name.DECLARE @TableName AS VARCHAR(100) = ‘tblStudent’DECLARE @DropQuery AS VARCHAR(2000) = ”SELECT @DropQuery = @DropQuery +’ALTER TABLE [‘ + @TableName + ‘]DROP CONSTRAINT [‘ + name + ‘]; ‘FROM sys.More items…

What if I delete a row containing a foreign key to another table?

Second, as a one-time schema-alteration exercise, add the ON DELETE CASCADE referential action to the foreign key on the referencing table e.g. … Then, forevermore, rows in the referencing tables will automatically be deleted when their referenced row is deleted.

How do you update a table that has a foreign key?

Creating a foreign key with DELETE and UPDATE CASCADE rulesSelect the parent table and the primary key column in the parent table. … In the INSERT and UPDATE specifications, select Cascade for the delete rule.Click on Close and save the table in the designer.More items…•Jul 3, 2019

Is Cascade delete a good idea?

Cascading deletes should not cause unexpected loss of data. If a delete requires related records to be deleted, and the user needs to know that those records are going to go away, then cascading deletes should not be used. … In fact, I’ve never actually used a cascading delete to implicitly delete related records.

Can we delete records from multiple tables in a single query?

You can specify multiple tables in a DELETE statement to delete rows from one or more tables depending on the particular condition in the WHERE clause. However, you cannot use ORDER BY or LIMIT in a multiple-table DELETE.

Can a table have both primary key and foreign key?

Primary keys always need to be unique, foreign keys need to allow non-unique values if the table is a one-to-many relationship. It is perfectly fine to use a foreign key as the primary key if the table is connected by a one-to-one relationship, not a one-to-many relationship.

What is Cascade delete in MySQL?

ON DELETE CASCADE clause in MySQL is used to automatically remove the matching records from the child table when we delete the rows from the parent table. It is a kind of referential action related to the foreign key.

Can foreign key be deleted?

A foreign key with cascade delete means that if a record in the parent table is deleted, then the corresponding records in the child table will automatically be deleted. … A foreign key with cascade delete can be created using either a CREATE TABLE statement or an ALTER TABLE statement.

What does drop table do in SQL?

We use the SQL DROP Table command to drop a table from the database. It completely removes the table structure and associated indexes, statistics, permissions, triggers and constraints. You might have SQL Views and Stored procedures referencing to the SQL table.