What's the difference between NO ACTION and RESTRICT?


With Firebird, there is no difference.

Some other SQL systems make a following distinction: NO ACTION means to allow the change if the new value in the child table is still valid after statement and all the triggers are completed (i.e. still found in the parent table of the relationship), while RESTRICT means that changing the value is not allowed at all (no change or delete is allowed if there are child records).

This is implemented in such way that NO ACTION constraint rules are checked after all other operation, and RESTRICT is checked before any other operation. In current Firebird versions, both keywords are implemented as NO ACTION.

Please note that RESTRICT rule is applied when option is not give in the constraint. That is, if you run:

ALTER TABLE EMPLOYEE ADD CONSTRAINT INTEG_28
FOREIGN KEY (DEPT_NO) REFERENCES DEPARTMENT (DEPT_NO);

Since ON UPDATE and ON DELETE clauses are not given, it means ON UPDATE RESTRICT and ON DELETE RESTRICT.


Do you find this FAQ incorrect or incomplete? Please e-mail us what needs to be changed. To ensure quality, each change is checked by our editors (and often tested on live Firebird databases), before it enters the main FAQ database. If you desire so, the changes will be credited to your name. To learn more, visit our add content page.

If you are a commercial tool maker and your tool features a great way to handle the issue written about in this FAQ, please check out our advertisement page.



All contents are copyright © 2007-2017 FirebirdFAQ.org unless otherwise stated in the text.


Links   Firebird   News   FlameRobin   Home Inventory powered by FB  
Add content   Advertise   About  

Categories
 Newbies
 SQL
 Installation and setup
 Backup and restore
 Performance
 Security
 Connectivity and API
 HOWTOs
 Errors and error codes
 Miscellaneous