I imported data into a MariaDB database while foreign key constraint checks were disabled. Those checks were enabled afterwards. However, some data in the database seems to be corrupt in the sense that the foreign key constraints are not satisfied.
I tried to use the mysqlcheck tool to verify all tables, but this does not produce any error output. Also running CHECK TABLE someTable does not show any errors or warnings.
Still I can manually show data not being correct, for example by performing a query:
select count(*) from some_table where id not in (select id from related_table)
where some_table has a foreign key constraint to related_table by id.
How do I fix this?
Related
I have the problem similar to this one SQL Server foreign key conflict in a multi values statement? However, in sql server 2008.
While I am reading data from csv file, there is some id already not exist in parent and thus return this error:
INSERT statement conflicted with the FOREIGN KEY constraint
May I know if there is a way similar to MySQL insert ignore. Such that I can simply skip the problematic data.
I accept that if there is no method other than creating a stored procedure with a new temp table (insert into a table without foreign key first, and then re-insert with where foreign_id exists in (select id from parent)).
As I really cannot find any in documentation, asking for ensuring I didn't miss anything.
One general solution which comes to mind would be to temporarily turn off the foreign key constraints, and do the insert. Then, afterwards, you may run a cleanup script/query to remove or rectify child records which are pointing to parents which do not exist. Once your data is in good shape, then turn on the foreign key constraints again.
Read How can foreign key constraints be temporarily disabled using T-SQL? to learn how to disable/enable a foreign key constraint for a single table:
ALTER TABLE MyTable NOCHECK CONSTRAINT MyConstraint -- disable
ALTER TABLE MyTable WITH CHECK CHECK CONSTRAINT MyConstraint -- enable
I have an odd issue with foreign keys. I am trying to perform the following query:
ALTER TABLE [GroupMember] FOREIGN KEY ([Group]) REFERENCES [Group]([GUID])
Which gives me the following error:
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK__GroupMember__Group__0D25C822". The conflict occurred in database "x", table "dbo.Group", column 'GUID'.
I then verified the existing things, which I have confirmed are all ok:
Referenced table (dbo.Group) has a defined PRIMARY KEY on [GUID] column
Referencing table (dbo.GroupMember) has no [Group]-values which do not exist in [GUID]-column of dbo.Group-table
No similarly referencing foreign keys exist already
From here on, I experimented. Taking some rows in and out, wiping the table, truncating the table. What I can conclude so far:
If I wipe the referencing table using DELETE FROM [GroupMember]; then try to apply the FK constraint, I receive the same error message
If I truncate the referencing table using TRUNCATE TABLE [GroupMember];, I can apply the FK constraint without errors. Additionally, I am able to reinsert the exact same data after applying the FK constraint, without problems.
From this I can conclude that the data itself is not the problem. Can anyone make sense of this? Why am I able to apply the constraint after truncating the table, but not after deleting all records?
If you are using Microsoft SSMS check whether unchecking "Prevent saving changes that require table re-creation" solves the problem. You'll find this in Options > Designers > Table and Database Designers.
I have had similar issues that have been resolved by this. Let me know if it works or not.
Good luck.
I'm running the following queries on PostgreSQL 9.3:
CREATE TABLE "app_item"
(
"id" SERIAL NOT NULL PRIMARY KEY,
"location_id" UUID NOT NULL
);
CREATE INDEX app_item_e274a5da
ON "app_item" ("location_id");
ALTER TABLE "app_item"
ADD CONSTRAINT app_item_location_id_5cecc1c0b46e12e2_fk_fias_addrobj_aoguid
FOREIGN KEY ("location_id") REFERENCES "fias_addrobj" ("aoguid") deferrable
initially deferred;
Third query returns:
ERROR: relation "fias_addrobj" does not exist
app_item - table in first database
fias_addrobj - table in second database
How to do correct query with this databases?
A local table must be referenced
However, as stated within the below link, you could maybe use a trigger which uses a cross server join (facilitated by dblink) to simulate the built-in methods for constraining?
For instance, you could have a trigger set up that on INSERT, checks to see if a given FK exists to aid with enforcing referential integrity, or on DELETE to cascade
http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=101322
P.S. Would avoid this at all costs.
I've not had occasion to use this myself, but you might want to look into Foreign Data Wrappers, which are essentially the successor to dblink. In particular, postgres-fdw.
Once the general setup of the fdw is in place (steps 1-3 in the link above), you could create a foreign table via CREATE FOREIGN TABLE, defined like the table in your remote DB, and then use that table as part of the foreign key CONSTRAINT, and see if it works.
If that doesn't work, another option would be to have a process which ETL's the data (say, via a Python script) from the remote server over to the local server (say, on an hourly or daily basis, depending on the size), and then you would have a true local table to use in the foreign key CONSTRAINT. It wouldn't be real-time, but depending on your needs, may suffice.
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.
I have the following query which is adding contraint.
but in order to add, i want to check if this key has already been used or not?
ALTER TABLE HL7_MessageHierarchy
ADD CONSTRAINT fk_vMessageType FOREIGN KEY (vMessageType)
REFERENCES HL7_MessageType(vMessageType);
for example. if i have to add a column, i can easily check if the table exists in sysobjects and its respective column exists in syscolumns.
Is it possible to use the query multiple times without GO and without making any error indeed? if yes then how ???
[EDIT]
I don't know why my browser not allowing me to add comments so i am adding to Edit.
I want to check if there exists any foreign key with same name. so if there is no data even then the query can make problem because the key may already be existing. I want to run the above script clean (ofcourse resident data does matter but that is perhaps a straight forward check?)
[EDIT]
my bad, i must have known that version is important... I believe its 2005... (will love to know if someone can tell for other versions too)
I assume you mean
check the HL7_MessageHierarchy for values not inHL7_MessageType"
So, a query like this will tell you
SELECT *
FROM HL7_MessageHierarchy H
WHERE NOT EXISTS (SELECT *
FROM HL7_MessageType T
WHERE H.vMessageType = T.vMessageType)
Also, I'd recommend using WITH CHECK too
ALTER TABLE HL7_MessageHierarchy WITH CHECK ADD
CONSTRAINT fk_vMessageType FOREIGN KEY (vMessageType)
REFERENCES HL7_MessageType(vMessageType);
In SQL 2005, the recommended way of checking for the existence of objects is Catalog Views. The one you want is sys.foreign_keys:
IF NOT EXISTS ( SELECT * FROM sys.foreign_keys
WHERE name = 'fk_vMessageType' )
BEGIN
EXEC ('
ALTER TABLE HL7_MessageHierarchy
ADD CONSTRAINT fk_vMessageType FOREIGN KEY (vMessageType)
REFERENCES HL7_MessageType(vMessageType)
')
END
I have wrapped the creation in EXEC to avoid confusing the parser.