I'm having some trouble with a SQL Server 2005 database that seems like it's keeping a ghost constraint around. I've got a script that drops the constraint in question, does some work, and then re-adds the same constraint. Normally, it works fine. Now, however, it can't re-add the constraint because the database says that it already exists, even though the drop worked fine!
Here are the queries I'm working with:
alter table individual drop constraint INDIVIDUAL_EMP_FK
ALTER TABLE INDIVIDUAL
ADD CONSTRAINT INDIVIDUAL_EMP_FK
FOREIGN KEY (EMPLOYEE_ID)
REFERENCES EMPLOYEE
After the constraint is dropped, I've made sure that the object really is gone by using the following queries:
select object_id('INDIVIDUAL_EMP_FK')
select * from sys.foreign_keys where name like 'individual%'
Both return no results (or null), but when I try to add the query again, I get:
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "INDIVIDUAL_EMP_FK".
Trying to drop it gets me a message that it doesn't exist. Any ideas?
It means the data is wrong on creation of the FK
That is, you have "EMPLOYEE_ID" values in the INDIVIDUAL child table that don not exist in the parent EMPLOYEE table.
You could use ALTER TABLE ...WITH NOCHECK ADD CONSTRAINT... but then the FK is no use
Related
ALTER TABLE Student ADD CONSTRAINT CHK_Student_ID_LENGTH CHECK (LEN([ID]) between 12 and 14);
SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_NAME = 'CHK_Student_ID_LENGTH';
alter table Student drop constraint CHK_Student_ID_LENGTH;
I tried to add check constraint using the first statement. It gave me the below error.
[23000][547] The ALTER TABLE statement conflicted with the CHECK constraint "CHK_Student_ID_LENGTH". The conflict occurred in database, table "Student", column 'ID'.
I tried to check if there was any existing constraint with the same name. But I did not get any. Still I tried to drop the constraint. But then it gave the error:
CHK_Student_ID_LENGTH is not a constraint.
But still add constraint statement gives error saying it already exists. Where am I going wrong?
The error message is a little badly worded, but isn't saying what you think it's saying.
It's not saying that there's already a constraint with the same name. It's saying that the constraint is being violated. That means that there is data already in the table that doesn't meet the requirements of the new constraint you're trying to introduce.
You could use the NOCHECK option to create the constraint whilst allowing existing data to violate it. But this is frequently the wrong thing to do. It is usually more sensible to fix the existing data.
Specifying NOCHECK means that the constraint can't be used by the optimizer to eliminate redundant actions that the logic of the constraint would preclude.
You probably have some records in Your table that conflict with that new constraint.
Just find them and UPDATE/DELETE before adding a contraint.
SELECT *
FROM Student
WHERE LEN([ID]) between 12 and 14
Or try to add that constraint without checking existing values using WITH NOCHECK
ALTER TABLE Student WITH NOCHECK
ADD CONSTRAINT CHK_Student_ID_LENGTH CHECK (LEN([ID]) between 12 and 14);
Tip: In migration files I usually add this before adding a new constraint:
IF OBJECT_ID('CHK_Student_ID_LENGTH') IS NOT NULL
ALTER TABLE Student DROP CONSTRAINT CHK_Student_ID_LENGTH
IF OBJECT_ID('CHK_Student_ID_LENGTH') IS NULL
ALTER TABLE Student ADD CONSTRAINT ...
More about ALTER TABLE https://learn.microsoft.com/en-us/sql/t-sql/statements/alter-table-transact-sql?view=sql-server-ver15
I'm having problems adding a foreign key to an existing table where the foreign key can be null.
Say I have a user table and a data table. The data table already has a working foreign key on the "createdBy" colum to the user table ID column. I've just added a second column to the data table "EditedBy" that allows for null values (meaning the data record hasn't been edited). So all the existing records have NULL as the value for this column.
I am trying to make a foreign key between Data.EditedBy and User.Id, but when I try to apply it, I get the following error.
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_Data_User_EditedBy". The conflict occurred in database "Test", table "dbo.User", column 'Id'.
It seems like its having a problem with the NULL values in the data table, but NULL is an acceptable value for a foreign key.
What am I missing?
UPDATE:
Full statement is as follows
USE [Test]
GO
ALTER TABLE [dbo].[Data] WITH CHECK ADD CONSTRAINT [FK_Data_User_EditedBy] FOREIGN KEY([Id])
REFERENCES [dbo].[User] ([Id])
GO
Ok, I feel like an idiot. I was using Management studio to create the relationship, and after I posted the equivalent alter statement (which didn't work either), I realized I was trying to make a foreign key between the ID field of [data] and the ID field of [user].
Obviously that wont work.
I fixed the statement to use the correct field in the [data] table and all is well.
Trying to run :
ALTER TABLE [dbo].[Table1] ADD
CONSTRAINT [FK_Table1_ScenarioResult]
FOREIGN KEY ([ScenarioResultID]) REFERENCES [dbo].[ScenarioResult] ([ScenarioResultID]) ON DELETE CASCADE
Getting this error :
Msg 547, Level 16, State 0, Line 1
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_Table1_ScenarioResult". The conflict occurred in database "8362", table "dbo.ScenarioResult", column 'ScenarioResultID'.
I have checked :
Constraint does not already exist, and no other exists on same column
The values in the column match in both tables
Types of columns are the same
Tried a different name, also fails
On SQL Server 2008 R2
Any ideas what I could try?
In theory this might work:
ALTER TABLE [dbo].[Table1] WITH NOCHECK ADD
CONSTRAINT [FK_Table1_ScenarioResult]
FOREIGN KEY ([ScenarioResultID]) REFERENCES [dbo].[ScenarioResult] ([ScenarioResultID])
ON DELETE CASCADE
Not sure how you checked for integrity of existing values, but it should be:
SELECT COUNT(*) as Orphans FROM [dbo].[Table1] t
WHERE NOT EXISTS
(SELECT * FROM [dbo].[ScenarioResult] WHERE ScenarioResultID = t.ScenarioResultID)
If "Orphans" is greater then zero you need to clean the data before adding a constraint.
This one was baffling me aswell, and then the penny dropped.
I was trying to create a Foreign Key using "Database Diagrams" in SQL Server 2012, but it refused to let me as it claimed to clash with the foreign key I was trying to create. Huh ?
But, I had accepted the defaults to "Enforce foreign key constraint". But I already had data in the two tables I was attempting to create a foreign key for, and it was breaking the foreign key rule I was trying to make, so SQL Server was rejecting the new key.
The solution (in this particular case) was to change "Enforce foreign key constraint" to "No", or at least until I had cleaned up my data.
Hope this helps.
I had the same issue
I clear the data of the tables where i want to edit the content and add a new foreign key constraint and retry.
It works for me.
I hope it help you.
Consider we have two tables ProductType and ProductSizeGroup as below
ProductType
Id
Name
MaleSizeGroupId
FemaleSizeGroupId
ChildSizeGroupId
ProductSizeGroup
Id
Name
Each of MaleSizeGroupId, FemaleSizeGroupId and ChildSizeGroupId fields should be FKs to ProductSizeGroup.Id.
I add one using the following statement:
ALTER TABLE [dbo].[ProductType]
WITH CHECK ADD CONSTRAINT
[FK_ProductType_ProductSizeGroup_Male] FOREIGN KEY([MaleGroupId])
REFERENCES [dbo].[ProductSizeGroup] ([Id])
This works fine. I try to add the next using
ALTER TABLE [dbo].[ProductType]
WITH CHECK ADD CONSTRAINT
[FK_ProductType_ProductSizeGroup_Female] FOREIGN KEY([FemaleGroupId])
REFERENCES [dbo].[ProductSizeGroup] ([Id])
But I get the error:
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_ProductType_ProductSizeGroup_Female". The conflict
occurred in database "dbname", table "dbo.ProductSizeGroup", column
'Id'.
So there is conflict.. but what conflict? What should I be looking for?
That just means: there are rows in your table ProductType that have values in the FemaleGroupId column which do not exist in the referenced table (ProductSizeGroup).
It's not a problem per se - you can totally have multiple columns going from one table to another.
The problem is with the existing data - you have data in there that doesn't live up to that FK constraint. Fix that data and you should be fine.
To find those offending rows, use a query like this:
SELECT *
FROM [dbo].[ProductType]
WHERE FemaleGroupId NOT IN (SELECT DISTINCT Id FROM [dbo].[ProductSizeGroup])
That will list all offending rows - update their attribute and get going again!
I'm currently reading through this Yii application eBook: http://www.packtpub.com/agile-web-application-development-yii11-and-php5/book - and I'm having a problem inputting the tutorials DDL / SQL statements into PHPMyAdmin without it throwing up errors.
Would someone be kind enough to shed some light on why the following syntax is invalid? It might be something simple but I can't see it:
SQL statement:
ALTER TABLE tbl_issue
ADD CONSTRAINT FK_issue_project FOREIGN KEY (`project_id`)
REFERENCES tbl_project(`id`) ON DELETE CASCADE ON UPDATE RESTRICT;
ALTER TABLE tbl_issue
ADD CONSTRAINT `FK_issue_owner` FOREIGN KEY (`owner_id`)
REFERENCES tbl_user(`id`) ON DELETE CASCADE ON UPDATE RESTRICT;
ALTER TABLE tbl_issue
ADD CONSTRAINT `FK_issue_requester` FOREIGN KEY (`requester_id`)
REFERENCES tbl_user(`id`) ON DELETE CASCADE ON UPDATE RESTRICT;
ALTER TABLE tbl_project_user_assignment
ADD CONSTRAINT `FK_project_user` FOREIGN KEY (`project_id`)
REFERENCES tbl_project(`id`) ON DELETE CASCADE ON UPDATE RESTRICT;
ALTER TABLE tbl_project_user_assignment
ADD CONSTRAINT `FK_user_project` FOREIGN KEY (`user_id`)
REFERENCES tbl_user(`id`) ON DELETE CASCADE ON UPDATE RESTRICT;
INSERT INTO tbl_user (`email`, `username`, `password`)
VALUES
(`test1#notanaddress.com`,`Test_User_One`, MD5(`test1`)),
(`test2#notanaddress.com`,`Test_User_Two`, MD5(`test2`));
Error Message
Error
SQL query:
ALTER TABLE tbl_issue
ADD CONSTRAINT FK_issue_project FOREIGN KEY ( `project_id` )
REFERENCES tbl_project( `id` ) ON DELETE CASCADE ON UPDATE RESTRICT ;
MySQL said:
#1005 - Can't create table 'trackstar_test.#sql-c78_127' (errno: 121) (<a
href="server_engines.php?engine=InnoDB&page=Status&
token=252c0553975923580ca430b6e98c4243">Details...</a>)
Note:
All the tables in the database are set to innodb as their storage engine.
I've tried using different foreign key names for each FK, still get the same error.
Update:
After finding no solution to the problem, I deleted by DB, uninstalled Xampp and then redid everything again. Seems to work now. Sorry to not be able to tell future readers exactly what the cause was, but it was most probably to do with my Database config or the information I added to it.
Actual Problem is :
AS you are Following the book, there are a few insert/ update statements are executed on
tbl_proect,
tbl_issue
than you are trying to add Foreign Key Constraint. that checks the table data before applying. So, Here is the actual mistake, may be your tables contain a few records that violate the foreign key constraints. hence phpmyadmin doesnot allow you to alter table and generates error message.
Solution :
TRUNCATE TABLE `tbl_project`
TRUNCATE TABLE `tbl_issue`
Do Only one thing, clear all the tables . Empty tables. . And here's your problm resolved now phpmyadmin allows you to run commands.