I have a table Person which contains 2 fields.In my another database i have a Participant Table(also have 2 columns).From Participant Table i have to insert values into Person Table.
but before every insertion,i want truncate the person Table.
I have try it out with linking Execute Sql task to Data flow task.But it is showing error that a Primary Foreign key relation exists there.
If I understand correctly, SSIS has nothing to do with your real problem, which is that you want to truncate a table that is referenced by a foreign key constraint. That question has already been answered: Cannot truncate table because it is being referenced by a FOREIGN KEY constraint?
If a table in sql server has foreign key references then you can't truncate. instead in your execute sql task use delete without a where clause.
delete from person_table
If you are really adamant about truncating the table, you could drop the foreign key constraints, then truncate the table then recreate the foreign key constraints. Providing of course, that the user you are running the package as has the privileges to do so.
Create an "Execute SQl" task and run DELETE FROM person
after this task, run your import.
DELETE FROM will give the same result as TRUNCATE TABLE, but if the table has a foreign key pointing to it, it cant be truncated. You have to use the delete command
You won't be able to delete either unless cascading deletes is turned on (or you delete the child records first). Why is this a problem you ask, why can't I do what I want to do? Because if you do then you may lose the integrity of the data. Suppose I have records in table2 which relate to records in table 1. Suppose further that table1 has an autogenerated id. If I could truncate that table, then I leave those records i ntable 2 hanging out without any record to reference them, they have become orphaned. Well but I'm putting the data back in you say. But then they will have new id numbers and you will still lose the relatinoship tothe related data.
Can you drop the FK and truncate and insert and recreate the FK. Yes you can but it is a poor practice and you should not unless you are also recreating those related records.
The best practice is to use a MERGE statement to update or insert depending on what you need.
In SSIS Transfer SQL Server Objects Task Set Property DeleteFirst to TRUE
Related
I am setting up a kind of test database in Microsoft SQL Server Express 2017. I have one main table with 10 columns, which is linked to 6 others, ie its primary key is the foreign key of 6 other tables.
I have populated this main table with just one record.
I need to truncate it - ie delete all the rows but not the table. I tried both truncate table and delete from but both take forever: after 4 minutes the query was still executing! I understand there are keys to check etc, but it's only one record. All the other tables are empty. This doesn't seem right. Any ideas what could be wrong and what I can do to fix it?
In response to the comment
It is probably uncommitted transactions, on your child tables.
You would first be deleting all the child records prior to deleting the parent table record. Is the child tables all empty?.
Do you have any uncommitted transactions in any of those tables? If you do then attempt to kill those sessions by engaging a dba.
A table that has foreign key constraints can't be truncated. Either you drop constraint, truncate table then re-create constraints Or make use of delete cascade. here is a link for same.
TRUNCATE TABLE is a DDL command, it cannot check to see whether the records in the table are being referenced by a record in the child table. In case of DELETE, database is able to make sure that it isn't being referenced by another record.
I want to delete a user form 'dbo.Gebruiker' when I run my query I get this error message.
The DELETE statement conflicted with the REFERENCE constraint
"FK_Klant_Gebruiker_beheerderid". The conflict occurred in database
"Planning", table "dbo.Klant", column 'BeheerderId'.
After reading on the forum, they said that first I have to remove from other table so when I run my query, again I get another message
The DELETE statement conflicted with the REFERENCE constraint
"FK_Gebruiker_Klant". The conflict occurred in database "Planning",
table "dbo.Gebruiker", column 'KlantId'.
When I run this query to see if that columns exists
select * from dbo.Gebruiker where
KlantId='1CA25570-1A02-42FC-836D-4897B95EF44A'
it does not show anything.
After reading on google and on forums they say that first I have to delete the foreign key constraint.
I'm also putting the helpConstraint
What would be best way to delete a user from "dbo.Gebruiker" please?
GebruikerTable and Dependencies
KlantTable and Dependencies
In general terms, if you want to delete a row whose id is a FK in another table and you are not using an automated DELETE rule (like CASCADE), then you need to do something with the rows on the dependent table(s) before the database will allow you to perform the DELETE.
It seems that this your problem, so you need to consider what to do with the rows of the dependent table(s) that currently refer to the key value of the row you intend to delete.
How do you delete values with a relational database for connected tables.
Example of Movie Database:
Movie Table -> Movie_has_Genre Table -> Genre Table
If I delete a Movie I would want to delete all the rows of Movie_has_Genre table where the foreign key is the same as the id from the movie table.
Should I be using a Trigger on the Movie table (on delete... do a delete on the relational table) or is there some other built in function to handle this?
I just vaguely recall there was another way to do this but cannot remember what it was called.
You use the cascade delete statement. It's syntax looks like this:
ALTER TABLE dbo.T2
ADD CONSTRAINT FK_T1_T2_Cascade
FOREIGN KEY (keyId) REFERENCES dbo.T1(keyId) ON DELETE CASCADE
The complete syntax is: here
There is an option in SQL Server to do this automatically via CASCADE settings as already shown.
This is a really handy option but make sure you don’t apply it to all of your tables that have foreign key references as it might cause unexpected loss of data. Make sure to thoroughly analyze weather this won’t cause any damage.
Another option is to use multiple delete statements starting from the tables that are referenced first.
I have an issue related to data in sql server. In my database some of the constraint were not enabled i.e. they were not checked , After some time working on it we found this issue that a parent rows can be deleted without deleting child, which was an issue. I enabled all the constraint in the database using query
ALTER TABLE tbl_name CHECK CONSTRAINT ALL
above query was executed on all the tables of that database without any error . But my concern is whether it will work or not , if it will work on the existing data then what will happen to that data whose parent table data has been deleted.
I want to know is there any way such that I can validate such data data whose parent record doesn't exist in the entire database. There are about 270 constraint containing FOREIGN KEY AND UNIQUE KEY . I don't want to go for manual option.
Please help me out.
ALTER TABLE tbl_name CHECK CONSTRAINT ALL
only re-enables the constraints. Importantly, the constraints are not checked against the existing data in the database (nor are they trusted by the optimizer). If you want that to occur, you need to specify WITH CHECK as well:
ALTER TABLE tbl_name WITH CHECK CHECK CONSTRAINT ALL
(And yes, the word CHECK appears twice)
If you execute this, and there are orphaned child rows (or other invalid constraints), then the ALTER TABLE will fail with an error message. There's nothing SQL Server can do to fix this issue - it's for you to decide whether to a) remove the orphaned rows, or b) to re-create, in some manner, a suitable parent row for them.
You can also add the 'ON DELETE CASCADE' code to the end of foreign keys to prevent orphaned child rows from persisting.
This is more of a 'better practice' going forward than a solution, but I believe Damien_The_Unbeliever has answered your main question.
Straight out of the MSDN docs for Sql Server 2005:
You cannot use TRUNCATE TABLE on tables that:
Are referenced by a FOREIGN KEY constraint.
Participate in an indexed view.
Are published by using transactional replication or merge replication.
I want the effect of a TRUNCATE (specifically the fact that it resets IDENTITY type columns), but I can't use one in my case because my table is referenced by a foreign-key elsewhere in the database.
Update: This is for a testing configuration where I am clearing out the referencing table as well, so foreign-key integrity is a non-issue.
What other ways are there to get around this?
You can delete all the rows and then do a DBCC CHECKIDENT (Tablename, RESEED, 0) to reset the identity seed
But again DELETE is fully logged while TRUNCATE is minimally logged and will be many times faster
Another option is to drop the foreign key constrains then do a truncate and then recreating the foreign key constraints
The fact that it is refernced by a foreign key is the clue you need to not truncate a table or you would be creating orphaned records. This is why truncate table is not allowed if a foreign key exists.
The correct process is to first delete the refernced records, if any, then drop the FK constraint, then truncate the table then reinstate the fk constraint. If you skip step one, you will create a data integrity nightmare where the record pointing to oldid 100 is not pointing to the new record that happens to get assigned to 100 and it isn;t the record it should match to.
You can drop the foreign key, truncate the table, and then recreate the foreign key.
You will need to drop the constraint, trunc the table, and then add the constraint back. However, you should be very careful with this. If there are rows in the table that you are dropping the FK reference to you will not be able to add it until those rows are deleted or the FK column in the other table is clear.