I am trying to alter table product to add a constraint of type foreign key for field petCat_ID so that it references table petCategory(ID). I just created table petCat_ID and i am getting a "Cannot add or update a child row" error.
This is the commands I performed to get this error:
Alter table product
-> ADD CONSTRAINT FK_petCatID
-> FOREIGN KEY (petCat_ID)
-> REFERENCES productCategory(ID);
Any help or tips would be greatly appreciated! Note: petCat_ID is in table product and productCategory is a different table.
In my comments I've mentioned that I need a clearer idea of what kind of database structure you have, but I have a series of things that will help you work through the problem you're having.
If an ALTER statement isn't working, and you have good syntax, it is because what you are doing conflicts with an already present rule.
Sometimes, doing a DROP TABLE command, followed by creating the table again can fix problems. This can be problematic if there are dependencies that keep you from dropping the table.
When things get dire, try looking at the script you used to make the DB in the first place. Modify it and see if you can get the properties you want. Once you do, make a new database table structure and migrate your table entries over to the new database from the old one.
I made a github repository here wherein I made a third normal form version of what the customer facing Amtrack database would look like, and even wrote scripts to add data to the tables, with examples. There are images showing the ER structure. I included my creation script, broken into each table's creation in specific order. It should be a good reference for how to assign table relationships, and that will give you a good idea of what you can alter. Disclaimer I wrote it for SSMS, but I don't believe I used anything SSMS specific I THINK that code should work in MySQL.
I'm trying to drop a table containing several hundred thousand column-based records. Normally when creating the database I use a column-based engine (infinidb) but in this case I forgot to include the ENGINE statement. So the database is pretty much unusable for my needs. Now I have a database full of tables that are taking forever to drop (it's been two hours and nothing has happened). I tried the ALTER TABLE table ENGINE=INFINIDB command but again, it's taking forever (see above re: two hours). EDIT: The first command I tried was DROP TABLE. It hung with every single table. Then I tried the ALTER command in case that was faster for some reason, but it wasn't.
Is there another way to get rid of this database? E.g. manually going into the /mysql/ directory and deleting the database? I guess I could just rename it and leave it, but I'd rather get rid of it entirely so it's not taking up space.
First of all you said Can't drop table. But in post you mentioned ALTER TABLE table ENGINE=INFINIDB.
But DROP != ALTER it is two different things.
So you can do following:
CREATE new table with same structure but engine you need.
copy(UPDATE) data from old table to the one you just created.
DROP old table.
RENAMErename new one to old name
It turned out that another process (a website) was using this database and had a couple of queries that got 'stuck' in the SQL server and caused the table to hang due to the database using the wrong engine, which I'm assuming was InnoDB since I didn't specify an engine when I initially used the "CREATE TABLE table1 AS SELECT * FROM table2" command. We finally managed to wipe the database and start over. Thanks for your help.
I am working on a web application using entity framework and MySql. I have created some views and tables in my database but unfortunately ADO.Net data modal is not including the views. I have recreated my data modal but still views are missing. I have applied several solutions which i have found on different forums some one was suggesting to restart visual studio, Even some people was asking to restart the PC. but its not working for me.
Finally i have managed to solve this problem by adding a primary key column in my select statement.It was obvious that we must need a primary key to add our table in modal but as views have no primary key that's why i was confused. In short we must have to include at least one primary key column of a table in select statement.
I have already existing DataBase inside SQL server 2008 around (300 tables) so I faced the following problems when i try to create an entity framework .edmx file:
If I specify to map all the 300 tables at once, the visual Studio will hang.
So I decide to include only the tables which I currently need, then the mapping will work fine. But if after that I add a new table to them, a Foreign key error will occur. So I have to delete the existing models and add them again with the new table. So the FK error will be removed.
So can anyone advice on how to overcomes these problems?
The error I usually got when adding a new table to the .edmx file will look something similar to.
Problem in mapping fragments starting at lines 2186, 2265:Foreign key constraint 'SDOrgPostalAddr_FK2' from table SDOrgPostalAddr (POSTALADDR_ID) to table AaaPostalAddress (POSTALADDR_ID):: Insufficient mapping: Foreign key must be mapped to some AssociationSet or EntitySets participating in a foreign key association on the conceptual side.
while if I added the table from the beginning then no error will be displayed.
Regards
I need the sample program in Java for keeping the history of table if user inserted, updated and deleted on that table. Can anybody help in this?
Thanks in advance.
If you are working with Hibernate you can use Envers to solve this problem.
You have two options for this:
Let the database handle this automatically using triggers. I don't know what database you're using but all of them support triggers that you can use for this.
Write code in your program that does something similar when inserting, updating and deleting a user.
Personally, I prefer the first option. It probably requires less maintenance. There may be multiple places where you update a user, all those places need the code to update the other table. Besides, in the database you have more options for specifying required values and integrity constraints.
Well, we normally have our own history tables which (mostly) look like the original table. Since most of our tables already have the creation date, modification date and the respective users, all we need to do is copy the dataset from the live table to the history table with a creation date of now().
We're using Hibernate so this could be done in an interceptor, but there may be other options as well, e.g. some database trigger executing a script, etc.
How is this a Java question?
This should be moved in Database section.
You need to create a history table. Then create database triggers on the original table for "create or replace trigger before insert or update or delete on table for each row ...."
I think this can be achieved by creating a trigger in the sql-server.
you can create the TRIGGER as follows:
Syntax:
CREATE TRIGGER trigger_name
{BEFORE | AFTER } {INSERT | UPDATE |
DELETE } ON table_name FOR EACH ROW
triggered_statement
you'll have to create 2 triggers one for before the operation is performed and another after the operation is performed.
otherwise it can be achieved through code also but it would be a bit tedious for the code to handle in case of batch processes.
You should try using triggers. You can have a separate table (exact replica of your table of which you need to maintain history) .
This table will then be updated by trigger after every insert/update/delete on your main table.
Then you can write your java code to get these changes from the second history table.
I think you can use the redo log of your underlying database to keep track of the operation performed. Is there any particular reason to go for the program?
You could try creating say a List of the objects from the table (Assuming you have objects for the data). Which will allow you to loop through the list and compare to the current data in the table? You will then be able to see if any changes occurred.
You can even create another list with a object that contains an enumerator that gives you the action (DELETE, UPDATE, CREATE) along with the new data.
Haven't done this before, just a idea.
Like #Ashish mentioned, triggers can be used to insert into a seperate table - this is commonly referred as Audit-Trail table or audit log table.
Below are columns generally defined in such audit trail table : 'Action' (insert,update,delete) , tablename (table into which it was inserted/deleted/updated), key (primary key of that table on need basis) , timestamp (the time at which this action was done)
It is better to audit-log after the entire transaction is through. If not, in case of exception being passed back to code-side, seperate call to update audit tables will be needed. Hope this helps.
If you are talking about db tables you may use either triggers in db or add some extra code within your application - probably using aspects. If you are using JPA you may use entity listeners or perform some extra logic adding some aspect to your DAO object and apply specific aspect to all DAOs which perform CRUD on entities that needs to sustain historical data. If your DAO object is stateless bean you may use Interceptor to achive that in other case use java proxy functionality, cglib or other lib that may provide aspect functionality for you. If you are using Spring instead of EJB you may advise your DAOs within application context config file.
Triggers are not suggestable, when I stored my audit data in file else I didn't use the database...my suggestion is create table "AUDIT" and write java code with help of servlets and store the data in file or DB or another DB also ...