Is there a setting in derby, for example an sql query ala "SET DATABASE REFERENTIAL INTEGRITY FALSE" where i can turn on and off referential integrity?
If you have a constraint that you don't wish to enforce, you can use DROP CONSTRAINT to drop it.
I frequently drop a constraint for a period of time while I am re-structuring my database, then re-add the constraint subsequently when I have the new data arranged as I want it.
According to this post on the mailing list (from 2006) it is not possible:
http://www.mail-archive.com/derby-user#db.apache.org/msg05345.html
I couldn't find anything in the manual either.
And the list of jdbc parameters has nothing, too.
Related
Is there a way for constraints to actually work in Snowflake?
A primary key is created. Still duplicates can be inserted in the table. Giving options like cascade update and delete cascade are not working with Foreign key
Can someone please help?
if you read the Snowflake documentation you will see that only NOT NULL constraints are enforced, all other constraint types are informational only.
I am guessing that the reason for this is that Snowflake is an analytical, rather than an OLTP, database and therefore the expectation is that constraints are enforced in your ELT processes (as is normal practice) rather than in the DB.
Snowflake does not enforce constraints except not null.
Snowflake Notes . I think we cannot enforce a constraint in snowflake database but you can apply the constraint in your ETL tool(if using)
Is there any easier way to change the collation on columns with foreign key constraints than manually removing them and adding them back up?
I have tried the disabling of the constraints without luck with the statement:
ALTER TABLE PM_Minnekorter NOCHECK CONSTRAINT ALL
Is it possible to automate the dropping of the constraints and recreation of them again? or is it any other better solutions?
Well we cannot change collation of column which are referenced.
It is clearly mentioned in this link https://msdn.microsoft.com/en-us/library/ms190920.aspx.
As far as automate dropping and creating question is concerned we can do that.
You can see it here. [the code is already exlained and available so giving it]
https://www.mssqltips.com/sqlservertip/3347/drop-and-recreate-all-foreign-key-constraints-in-sql-server/
I'm trying to insert initial data into a DB2 database in DbUnit using DatabaseOperation.INSERT.execute(...) which works fine with some datasets. In order to insert some datasets however, I need to disable foreign key constraints first (because the tables in some datasets can be listed in a 'wrong' order).
I'm disabling the foreign key constraints with command SET INTEGRITY FOR <table_name> OFF, but when I try to insert the data after calling that command, I get this error:
com.ibm.db2.jcc.am.SqlException: DB2 SQL Error: SQLCODE=-668, SQLSTATE=57016, SQLERRMC=1;SCHEMA.TABLE, DRIVER=4.17.30
The IBM error code explanation isn't much helpfull here. Is there something I need to do after setting integrity on a table and before inserting data into that table?
EDIT:
I found this in the documentation for the OFF statement: "Specifies that the tables are placed in set integrity pending state. Only very limited activity is allowed on a table that is in set integrity pending state."
If I understand it correctly, this means that when I turn off the integrity checks on a table, I cannot perform any write/modify operations on it! What's the point of turning the integrity check off then? I need to find a way to do this.
You are not "disabling the foreign key constraints with command SET INTEGRITY". SET INTEGRITY OFF basically means "I'm not sure about the integrity of this table data, so I'd rather restrict access to it until I figure out what's wrong".
To temporary disable foreign key verification you might try ALTER TABLE foo ALTER FOREIGN KEY bar NOT ENFORCED.
Hi I've set up two very basic tables. One table will act as a look up, with an identity field as a primary key. The other table uses the look up ID as a foreign key.
I have created a relationship constraint so now I cannot delete from the look up if the foreign key is used in the "main" table.
However my issue is i can add a record with a foreign key that doesn't exist.
To my way of thinking this shouldn't be allowed, can anyone tell me what setting I need to use to enforce this and whether this is typical database design or not?
Thanks Dave
You way of thinking is correct. Good database design provides some way of enforcing what is called "Referential Integrity". This is simply a buzzword for the concept you have derived on your own. Namely that a foreign key should be rejected if it refers to a non existent row. For a general discussion of referential integrity, see the following Wikipedia article. It's short.
http://en.wikipedia.org/wiki/Referential_integrity
Some pprogrammers would like to enforce referential integrity inside their programs. In general, it's a much better plan to define a referential integrity constraint inside the database, and let the DBMS do the enforcement. It's easier, it's faster, and it's more effective.
The SQL Data Definition Language (DDL) provides a way to declare a foreign key constraint when you create a table. The syntax differs a little between different dialects of SQL, but it's basically the same idea in all of them. Here's a capsule summary.
http://www.w3schools.com/sql/sql_foreignkey.asp
The documentation for SQL Server should have a description of the referential integrity constraint under the CREATE TABLE command.
i am using linq to sql .dbml ,
May i know what is the best way to add foreign key constraint to the database?
ALTER TABLE Staffs
Add CONSTRAINT fk_Staffs FOREIGN KEY(UserId) REFERENCES Users(Id);
i can write this with no problem. But when my database table increases, i have hard time to maintain the Add Constraint foreign script . Each time when i have multiple update to the database columns, then i will crack my head to update those alter table script.
Could there be a simple process for this? In the .dbml, i can drag and drop the association to add the foreign key, i wonder is there a way that i can export those foreign key into script which like what i wrote above? this is good when i want to do the deployment.
Or must i write the alter script and update it whenever there is changes on tables?
please advice
You only need to do this once per database update that actually changes a FK relationship.
In the context of doing a database refactoring this is usually not a big deal of the whole refactoring.
But if you don't like writing your scripts you can use the table designer i SQL Management Studio.
Right click table -> Design
Right click on the appropritate database column (one of the rows in the designer) -> Relationships
In the dialog, add a new relationship and select related tables and columns in the properties editor.
Done.
This is the right way to do it. You can also do it in the designer as written in another answer here but that way if you have to promote from development to production you must do it all by hand and that is very tedious and can easilly lead to errors.
A compromise can be to use the designer to do the changes and in SQL management studio use the right mouse click and select `Script object...ยด. Than you do not have to type that much.
You mention a change of table names. Well, that should not happen that often!
If it happens a lot, I advise you to create some naming conventions with your team about how to name your columns (and stick to them) and the amount of work will be limited.