Asked by: Vivian Soussi
technology and computing databases

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

To delete a foreign key constraint
  1. In Object Explorer, expand the table with the constraintand then expand Keys.
  2. Right-click the constraint and then clickDelete.
  3. In the Delete Object dialog box, click OK.

Keeping this in view, can we delete a foreign key?

A foreign key with cascade delete meansthat if a record in the parent table is deleted, thenthe corresponding records in the child tablewill automatically be deleted. A foreign keywith cascade delete can be created using either a CREATETABLE statement or an ALTER TABLE statement.

Beside above, what is foreign key constraint in SQL Server? SQL FOREIGN KEY Constraint. A FOREIGN KEYis a key used to link two tables together. A FOREIGNKEY is a field (or collection of fields) in one table thatrefers to the PRIMARY KEY in another table. The FOREIGNKEY constraint is used to prevent actions that would destroylinks between tables.

how do I delete a constraint in SQL Server?

Using SQL Server Management Studio

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

How do I cascade delete in SQL Server?

To add "Cascade delete" to an existing foreignkey in SQL Server Management Studio: First, select yourForeign Key, and open it's "DROP and Create To.." in a new Querywindow. Then, just add ON DELETE CASCADE to the ADDCONSTRAINT command: And hit the "Execute" button to run thisquery.

Related Question Answers

Chaymaa Lindacher


How do I remove a foreign key from a table?

To delete a foreign keyconstraint
In Object Explorer, expand the table with theconstraint and then expand Keys. Right-click the constraintand then click Delete.

Bobo Dhrtiman


Can a foreign key be null?

Short answer: Yes, it can be NULL orduplicate. I want to explain why a foreign key might need tobe null or might need to be unique or not unique. Firstremember a Foreign key simply requires that the value inthat field must exist first in a different table (the parenttable). Null by definition is not a value.

Valvanera Kantauriko


What is the difference between primary and foreign keys?

Key Differences between Primary key andForeign key
A primary is a set of attributes/a candidatekey that distinctly identifies a record in arelation. However, a foreign key in a table refers to theprimary key of another table. However, foreign keyconstraint can not be applied to the temporarytables.

Merouane Fiorito


Aissata Bajenoff


How do I delete a foreign key in Oracle?

Oracle / PLSQL: Drop a Foreign Key
  1. Description. Once a foreign key has been created, you may findthat you wish to drop the foreign key from the table.
  2. Syntax. The syntax to drop a foreign key in Oracle/PLSQL is:ALTER TABLE table_name DROP CONSTRAINT constraint_name;
  3. Example. If you had created a foreign key as follows:

Magdalene Budzis


Can primary key be null?

SQL PRIMARY KEY Constraint. Primary keysmust contain UNIQUE values, and cannot contain NULL values.A table can have only ONE primary key; and in thetable, this primary key can consist of single or multiplecolumns (fields).

Manuel Niegmann


What is foreign key in database?

A foreign key is a column or group of columns ina relational database table that provides a link betweendata in two tables. It acts as a cross-reference between tablesbecause it references the primary key of another table,thereby establishing a link between them.

Aracelys Hoppener


What is foreign key SQL?

SQL > Constraint > Foreign Key. Aforeign key is a column (or columns) that references acolumn (most often the primary key) of another table. Thepurpose of the foreign key is to ensure referentialintegrity of the data. In other words, only values that aresupposed to appear in the database are permitted.

Ravi Giroes


How do you delete a column?

In MySQL, the syntax for ALTER TABLE Drop Columnis,
  1. ALTER TABLE "table_name" DROP "column_name";
  2. ALTER TABLE "table_name" DROP COLUMN "column_name";
  3. ALTER TABLE Customer DROP Birth_Date;
  4. ALTER TABLE Customer DROP COLUMN Birth_Date;
  5. ALTER TABLE Customer DROP COLUMN Birth_Date;

Omega Viselov


How delete a row in SQL?

To remove one or more rows in a table:
  1. First, you specify the table name where you want to remove datain the DELETE FROM clause.
  2. Second, you put a condition in the WHERE clause to specifywhich rows to remove. If you omit the WHERE clause, the statementwill remove all rows in the table.

Conceso Baban


What are SQL constraints?

Constraints are the rules enforced on the datacolumns of a table. These are used to limit the type of data thatcan go into a table. This ensures the accuracy and reliability ofthe data in the database. Constraints could be either on acolumn level or a table level.

Eugenijus Wasmut


How do I add a foreign key in SQL Server 2014?

Using SQL Server Management Studio
  1. In Object Explorer, right-click the table that will be on theforeign-key side of the relationship and click Design.
  2. From the Table Designer menu, click Relationships.
  3. In the Foreign-key Relationships dialog box, click Add.
  4. Click the relationship in the Selected Relationship list.

Ernestas Hofener


How do you drop an index?

The DROP INDEX command is used to delete an index in atable.
  1. MS Access: DROP INDEX index_name ON table_name;
  2. SQL Server: DROP INDEX table_name.index_name;
  3. DB2/Oracle: DROP INDEX index_name;
  4. MySQL: ALTER TABLE table_name. DROP INDEX index_name;

Chahd Rohwedder


What is on delete cascade?

A foreign key with cascade delete means that if arecord in the parent table is deleted, then thecorresponding records in the child table will automatically bedeleted. This is called a cascade delete inOracle.

Diago Ewerhart


How do I rename a column in SQL?

SQL Rename Column Syntax
  1. ALTER TABLE "table_name" Change "column 1" "column 2" ["DataType"];
  2. ALTER TABLE "table_name" RENAME COLUMN "column 1" TO "column2";
  3. ALTER TABLE Customer CHANGE Address Addr char(50);
  4. ALTER TABLE Customer RENAME COLUMN Address TO Addr;

Jenny Indaberea


How do you drop a unique constraint in Oracle?

Drop Unique Constraint
ALTER TABLE table_name DROP CONSTRAINTconstraint_name; table_name. The name of the table to modify. Thisis the table that you wish to remove the unique constraintfrom.

Lise Gojenola


How do you fix Ora 00001 unique constraint violated?

The option(s) to resolve this Oracle error are:
  1. Option #1. Drop the unique constraint.
  2. Option #2. Change the constraint to allow duplicatevalues.
  3. Option #3. Modify your SQL so that a duplicate value is notcreated. Note. If you are not sure which unique constraint wasviolated, you can run the following SQL:

Naouel Panet


Can a primary key be a foreign key?

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

Izeia Lourdes


What is data type in SQL?

In this article
A data type is an attribute that specifies thetype of data that the object can hold: integerdata, character data, monetary data, date andtime data, binary strings, and so on. SQL Serversupplies a set of system data types that define all thetypes of data that can be used with SQLServer.