CODEWITHSUNDEEP
databasecascadeuse-case
idiotdesi
idiotdesi

Reputation: 11

Cascade Delete Use Case

I am pretty new to Business Analysis. I have to write requirements that show both (for now) cascade delete (for two tables) and the rest of the tables will delete explicitly.

I need some guidance for how to write the requirements for cascade deletion.

Upvotes: 1

Views: 1036

Answers (3)

Gabriel Ščerbák
Gabriel Ščerbák

Reputation: 18570

You don't write use cases for functionality - that is the reason why it is hard to properly answer your question - we don't know the actor who interacts with the system and of course we know nothing about the system, so we cannot tell you how to write description of their interactions. You should write your use cases first and from them derive the functionality.

Upvotes: 0

Dennis
Dennis

Reputation: 4017

Use the ON DELETE CASCADE option to specify whether you want rows deleted in a child table when corresponding rows are deleted in the parent table. If you do not specify cascading deletes, the default behavior of the database server prevents you from deleting data in a table if other tables reference it.

If you specify this option, later when you delete a row in the parent table, the database server also deletes any rows associated with that row (foreign keys) in a child table. The principal advantage to the cascading-deletes feature is that it allows you to reduce the quantity of SQL statements you need to perform delete actions.

For example, the all_candy table contains the candy_num column as a primary key. The hard_candy table refers to the candy_num column as a foreign key. The following CREATE TABLE statement creates the hard_candy table with the cascading-delete option on the foreign key:

CREATE TABLE all_candy 
   (candy_num SERIAL PRIMARY KEY,
    candy_maker CHAR(25));

CREATE TABLE hard_candy 
   (candy_num INT, 
    candy_flavor CHAR(20),
    FOREIGN KEY (candy_num) REFERENCES all_candy
    ON DELETE CASCADE)

Because ON DELETE CASCADE is specified for the dependent table, when a row of the all_candy table is deleted, the corresponding rows of the hard_candy table are also deleted. For information about syntax restrictions and locking implications when you delete rows from tables that have cascading deletes, see Considerations When Tables Have Cascading Deletes.

Source: http://publib.boulder.ibm.com/infocenter/idshelp/v10/index.jsp?topic=/com.ibm.sqls.doc/sqls292.htm

Upvotes: 1

Andrey
Andrey

Reputation: 60065

  • Delete child entities on parent deletion.
  • Delete collection members if collection entity is deleted.

Actually it is hard to understand the task without context and also it smells like university/colledge homework (we had one very similar to this).

Upvotes: 1

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