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My Sql Foreign Key by koldaf(m): 5:42am On May 08, 2013 |
Hi pals, am currently working on a dbase and i need to declare a foreign key such dt an alteration in table A will take effect in table B. Please how do i write d code and putting the necessary constraints? Thanks in anticipation. |
Re: My Sql Foreign Key by DualCore1: 8:43am On May 08, 2013 |
I don't think that can be achieved with foreign keys. Infact what you want to do beats the need for a relational database. A relational database is one where tables relate to each other (using primary/foreign keys) and no two tables should contain the same chunk of information. In clear terms, you should build your database in such a way that information is central to one place and not redundant. You can do some Google'ing and also await other responses from people who may have something better to offer. |
Re: My Sql Foreign Key by spikesC(m): 10:43am On May 08, 2013 |
What is the alteration, how does the data in table A relate to table B. What is the tables all about? we need more details |
Re: My Sql Foreign Key by tabontabon: 12:47pm On May 08, 2013 |
Depending on what you want to achieve,you can use a stored procedure/function,a trigger or use the last insert id value from a previous insert query to update or do some other processing.send a mail to labegan at gmail dot com,with full details of what you want to do and probably your code structure |
Re: My Sql Foreign Key by yawatide(f): 4:38pm On May 08, 2013 |
Assuming I understand what you mean and assuming you are using mySQL: When you create a primary key in one table and a foreign key in another, the 2 tables are related. Now, if you delete from A, without a constraint, you will leave B "hanging" or "orphaned" in that the relationship b/w a particular row in A and a particular row in B is no more. To enforce the situation where what you update in A applies to B or what you delete in A applies to B, you need to use "ON DELETE CASCADE" and/or "ON UPDATE CASCADE" An example:
Again, the above assumes I understand what you need. Good luck! |
Re: My Sql Foreign Key by koldaf(m): 8:04pm On May 13, 2013 |
Thank u all 4 ur contributions, it has really helpd alot... Yewa-ti-de seems to get d true picture, thanks 4 ur contribution... A bow to all d oga in d house... |
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