mysql - ON DELETE CASCADE in this case? -


i need advice on whether on delete cascade suitable use in following table

create table category (     id int not null auto_increment primary key,     name varchar(255) not null,     maincategory int default null,     foreign key(maincategory) references category(id) on delete cascade on update cascade ) engine = innodb default charset = utf8;

in case, on delete cascade delete sub categories if main category gets deleted.is recommended approach ?

you trying create tabular representation of tree structure. using adjacency model, storing id of parent in maincategory field (usually called parent_id).

yes, approach totally valid. using on delete cascade securing delete anomalies.

i recommend read nested sets - efficient technique representing trees in sql:

http://www.evanpetersen.com/item/nested-sets.html

how represent data tree in sql?

http://en.wikipedia.org/wiki/nested_set_model

and book: joe celko "trees , hierarchies in sql smarties"


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