The discussion about foreign key constraint
lazarus / 31-LCL

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bugxiong · 2013-05-24 01:16

Today's Reading "SQL anti-patterns", inspired by many.
But one of the foreign key constraint to say, there are a few
Express their views.

Foreign key constraints, mainly used in
1 Make sure the insertion consistency, when inserting a foreign key as
the other tables in the table when the checks related to the primary
key of the table value exists.
(2) ensure that the update consistency, when the primary key is
modified, all foreign key is specified as Patron key table will be
updated.

I have a lot of system design is to avoid deletion, update the primary
key to avoid in order to avoid the above two problems.

In reality, a record to be deleted, will inevitably lead to
operational detail data deleted, even when using a foreign key
constraint can not be avoided,

Such as deleting a commodity information, then the corresponding data
inside the documents will be cascading deletes (using foreign key
associations)

Will result in loss of data. We take a look at why users want to
delete a product information,

from :http://www.fpccn.com/thread-2938-1-1.html

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BigChimp · 2013-05-24 06:56

Unless you disable cascaded deletes in your foreing key constraint of
course.... or if you actually need to have that linked information
deleted automatically.

Why not throw primary keys out the window while we're at it and let
data integrity be managed by application programs?
... Then we can use nice flat files for data storage