Question: How do you delete a child table in SQL?

How do you delete a child table record in SQL?

Two possible approaches.

  1. If you have a foreign key, declare it as on-delete-cascade and delete the parent rows older than 30 days. All the child rows will be deleted automatically.
  2. Based on your description, it looks like you know the parent rows that you want to delete and need to delete the corresponding child rows.

Can we delete child table?

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. This is called a cascade delete in SQL Server.

How do you delete a data table in SQL?

SQL DELETE

  1. First, you specify the table name where you want to remove data in the DELETE FROM clause.
  2. Second, you put a condition in the WHERE clause to specify which rows to remove. If you omit the WHERE clause, the statement will remove all rows in the table.

Can you delete any tuple in a child table?

ii. CASCADE option: delete all the tuples in the referencing tables (Child Tables) which have the primary key value of the deleted tuple.

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Can we delete data from parent without child table?

That means a row in Table A can’t be deleted if any row in Table B references that row. There is no way to get around this except to permanently remove the foreign key. The purpose of a foreign key is to prevent exactly this scenario.

Is deletion possible if the row to be deleted is referred in the child table?

3 Answers. It is possible with some agreements in your data. To maintain child table data you’ll have to do ON DELETE SET NULL . This will leave data, but set FK to NULL value (in child table).

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.

What is on delete no action?

NO ACTION means that nothing will happen when you delete from your Subject table to the Topic table. In that case, if there is a row in Topic for a given SubjectId you cannot delete from it without breaking referential integrity, so the Delete will be rolled back.

Is delete a DDL command?

DROP and TRUNCATE are DDL commands, whereas DELETE is a DML command. DELETE operations can be rolled back (undone), while DROP and TRUNCATE operations cannot be rolled back.

What is the SQL query to delete all rows in a table without deleting the table?

To delete every row in a table:

  1. Use the DELETE statement without specifying a WHERE clause. With segmented table spaces, deleting all rows of a table is very fast. …
  2. Use the TRUNCATE statement. The TRUNCATE statement can provide the following advantages over a DELETE statement: …
  3. Use the DROP TABLE statement.
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