My question is related to the ER-diagram I designed using Oracle SQL developer. I designed this ER-diagram but I don't know how to read the relationships between these tables.
I have created this ER diagram:
ER Diagram
As it can be seen that these relations don't look like those normal one to many or many to one relations. Can anyone please help me how to read the relation between SYS.GENERAL_LEDGER_ACCOUNTS and SYS.INVOICE_LINE_ITEMS? Thanks in advance
The relationship is described by the foreign key:
ALTER TABLE invoice_line_items
ADD CONSTRAINT line_item_fk_accounts
FOREIGN KEY (account_number)
REFERENCES general_ledger_accounts(account_number);
Defines a foreign key with the name line_item_fk_accounts on the column account_number which references the account_number of the general_ledger_accounts.
Assuming that it is notNULL then this is a many-to-one relationship such that each row of invoice_line_items has a relationship to exactly one row in the general_ledger_accounts and there can be many invoice_line_items for each general_ledger_accounts.
Similarly, line_items_fk_invoices is a many-to-one constraint with many invoice_line_items each referencing one row of the invoices table.
Aside: NEVER modify the system schemas. If you do you risk making the database unusable and invalidating any support contract that you have with Oracle. Instead, you should create a user and then work in that schema.
Related
Can someone suggest a way to generate delete queries for various tables linked via foreign key constrains for Oracle ? A solution for SQLServer is mentioned here
Copied description from the original question :
I have the table: DelMe(ID) and there are 30 tables with fk references
to its ID that I need to delete first, is there some tool/script that
I can run that will generate the 30 delete statements based on the FK
relations for me ?
I am wondering if a PL/SQL (oracle) table can carry three foreign keys? thanks in advance if any one can help me in this regard.
There is no explicit limit on the number of foreign keys on a table. However, there is a limit of 1000 columns per table, so that probably constitutes a practical limit.
Here is a SQL Fiddle which creates a toy table with five foreign keys.
There is not limit on foreign keys use except logic which based behind use of foreign keys, and if one table needs too much foreign keys, which is not logic wise, and database design suffers in such scenario.
As well as 1000-column constraint of oracle tables and pl/sql procedures also have limit in code.
I take Trains as one table and passenger as other table.
train table has train_no, train_name.
Passenger table has pnr and train_no.
i would like to create train_no as foreign key in passengers table.
please provide sufficient code for it..
i am rookie in it.
Thanks in advance
Parse is MongoDB like Object DBMS.
Concept of FK constraints is not available in Parse.
In order to use referencing you have to use Pointers. Although you can write some code for having FK constraint satisfaction (One easy option for the same is to use beforeSave feature of Cloud Code.)
I have a problem with grocery CRUD and "set_relation_n_n" function:
http://www.grocerycrud.com/documentation/options_functions/set_relation_n_n
I want the fields from "This Table", "Relation Table" and "Selection Table". There are any way to do that?. This is my schema (MySQL):
EDITED:
A few things (by the moment):
This table: timeline_events;
Relation table: timeline_events_options;
Selection table: timeline_events_tags;
id_timeline is the foreign key from another table (not showing in the image above), event_id is a field required for the widget I am using now. id_event is the foreign key from timeline_events, id_event_tags is the foreign key from timeline_events_tags.
Thank you very much for your answers :).
I believe you should repair your tables first. All three tables has primary key named id which could be id_timeline in timeline_events table; id_event in timeline_events_options table and id_tag in timeline_events_tags table. Considering this as your table fields, this should be the function.
$crud->set_relation_n_n('eventtags', 'timeline_events_options', 'timeline_events_tags', 'id_timeline', 'id_tag', 'tags','priority');
I don't guaranty it will work because I didn't test it but you can try this one.
The design of my database has a table named person and tables employee and student are specializations of the table person the relationship between tables is total and has an overlapping restriction.
The problem is that I want to insert a student or employee and that the parent table (person) is updated automatically but the DBMS says violated a referential integrity constraint
I am using oracle can someone help me?
If I understood you correctly you have one table per type (TPT) and an employee can never be a student and also the other way around.
I assume that your problem is that the constraint is checked immediately instead of using deferred checking. That means the constraints are checked when your transaction is finished - which gives you the possibility to insert an employee/student and let your trigger do its work and after that do the commit.
Information about deferred constraints:
Oracle documentation
More information