I have a simple two table relationships. Member, which can contain 0 or more Characters.
Here is the scheme:
CREATE TABLE IF NOT EXISTS 'main'.'member' (
'id' TEXT NOT NULL,
'platform_id' INTEGER NOT NULL,
PRIMARY KEY('id', 'platform_id')
);
CREATE TABLE IF NOT EXISTS 'main'.'character' (
'id' TEXT NOT NULL,
'member_rowid' INTEGER NOT NULL,
PRIMARY KEY('id', 'member_rowid'),
FOREIGN KEY ("member_rowid")
REFERENCES member ("rowid")
ON DELETE CASCADE
);
I then insert a member like so:
INSERT OR IGNORE into member ('id', 'platform_id') VALUES ("mid", 1);
select rowid from member;
which shows the rowid of 1.
However, when I try to insert into Character like so:
INSERT OR IGNORE into character ('id', 'member_rowid') VALUES ("cid", 1);
I get the following error:
Result: foreign key mismatch - "character" referencing "member"
At line 1:
INSERT OR IGNORE into character ('id', 'member_rowid') VALUES ("cid", 1);
Its not clear to me what is going on, since the rowid exists. Can I not use rowid as a foreign key?
I have seen some discussion around a foreign key having to reference the "entire primary key or unique key/index". I thought rowid satisfied that.
kFirst, you are using single quotes for identifiers. I strongly, strongly discourage you from doing this -- even if SQLite allows it. Only use single quotes for string and date constants.
Second, your foreign key is just really weird. It is sad that SQLite accepts it. The foreign key should be to the primary key. You can specify that rowid is the primary key -- fine. Then the other keys should be declared as unique.
Finally, the code you have works when I try it. Here is a db<>fiddle.
I'm trying to setup a many to many association on the same base table in postgres.
I'm a little stuck with this query; particularly the following error message.
Error
ERROR: insert or update on table "link" violates foreign key
constraint "link_primaryid_fkey" SQL state: 23503 Detail: Key
(primaryid)=(2) is not present in table "entity".
I would expect the PrimaryId column to exist in the Link table (Which it does). However the error seems to suggest the PrimaryId column also needs to exist in the base Entity Table which is what I'm trying to avoid.
Would anyone be able to point me in the right direction?
Script to get up to speed
--- Create Tables
CREATE TABLE "Entity" ("Id" SERIAL PRIMARY KEY);
CREATE TABLE "Task" ("Name" TEXT) INHERITS ("Entity");
CREATE TABLE "Project" ("Name" TEXT) INHERITS ("Entity");
--- Create mock data
INSERT INTO "Task" ("Name") VALUES ('Foo');
INSERT INTO "Project" ("Name") VALUES ('Bar');
-- Create Link Table
CREATE TABLE "Link" (
"PrimaryId" INTEGER REFERENCES "Entity" ("Id")
ON UPDATE CASCADE
ON DELETE CASCADE,
"SecondaryId" INTEGER REFERENCES "Entity"("Id" )
ON UPDATE CASCADE
ON DELETE CASCADE,
PRIMARY KEY ("PrimaryId", "SecondaryId")
);
--- Create Associations. It errors here
INSERT INTO "Link" ("PrimaryId", "SecondaryId") VALUES (2, 1)
Update 1
Updated to use absolute case (") everywhere
Thanks
Foreign keys do not work well with inheritance, as they only see the contents of the base table, not the inherited tables.
Please see https://www.postgresql.org/docs/9.6/static/ddl-inherit.html and specifically:
A serious limitation of the inheritance feature is that indexes (including unique constraints) and foreign key constraints only apply to single tables, not to their inheritance children. This is true on both the referencing and referenced sides of a foreign key constraint. Thus, in the terms of the above example:
(...)
Specifying that another table's column REFERENCES cities(name) would allow the other table to contain city names, but not capital names. There is no good workaround for this case.
I'll post only the main part. I have two tables, each one has to have the PK of the other as a FK.
CREATE TABLE apartment
(
cod_apartment INT NOT NULL PRIMARY KEY,
cod_offer INT NOT NULL
);
CREATE TABLE offer
(
cod_offer INT NOT NULL PRIMARY KEY,
cod_apartment INT NOT NULL
);
First I inserted the values on both tables and it was working, I could even search using "select * from...". But then I tried to add the foreign key:
This worked.
ALTER TABLE offer
ADD FOREIGN KEY (cod_apartment ) REFERENCES apartment;
And this not.
ALTER TABLE apartment
ADD FOREIGN KEY (cod_offer) REFERENCES offer;
This is the error message:
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK__apartment__cod_offer__6383C8BA". The conflict occurred in database "kleber_apartment", table "dbo.offer", column 'cod_offer'.
The problem is, every time I try to execute, the FK name changes. And this FK actually doesn't exist. I already dropped both tables and tried to insert the values again, but the same happens.
What could be?
That means you're trying to add a foreign key when existing data doesn't obey that constraint. So you have a record in your apartment table where the cod_offer column does not match any value in the cod_apartment table.
Adding a foreign key not only constrains future data, but it requires that any existing data must also follow the rule.
And regarding the 6383C8BA, whenever you add a constraint without giving it a name, SQL Server picks one for you. Personally, I'd recommend something like:
alter table dbo.apartment
add constraint FK_apartment__cod_offer
foreign key (cod_offer) references dbo.offer (cod_offer);
This lets you define names the way you want, and is a little more clear about what you're actually building.
Why does add a foreign key to the tblDomare table result in this error?
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK__tblDomare__PersN__5F7E2DAC". The conflict occurred in database "almu0004", table "dbo.tblBana", column 'BanNR'.
Code
CREATE TABLE tblDomare
(PersNR VARCHAR (15) NOT NULL,
fNamn VARCHAR (15) NOT NULL,
eNamn VARCHAR (20) NOT NULL,
Erfarenhet VARCHAR (5),
PRIMARY KEY (PersNR));
INSERT INTO tblDomare (PersNR,fNamn,eNamn,Erfarenhet)
Values (6811034679,'Bengt','Carlberg',10);
INSERT INTO tblDomare (PersNR,fNamn,eNamn,Erfarenhet)
Values (7606091347,'Josefin','Backman',4);
INSERT INTO tblDomare (PersNR,fNamn,eNamn,Erfarenhet)
Values (8508284163,'Johanna','Backman',1);
CREATE TABLE tblBana
(BanNR VARCHAR (15) NOT NULL,
PRIMARY KEY (BanNR));
INSERT INTO tblBana (BanNR)
Values (1);
INSERT INTO tblBana (BanNR)
Values (2);
INSERT INTO tblBana (BanNR)
Values (3);
ALTER TABLE tblDomare
ADD FOREIGN KEY (PersNR)
REFERENCES tblBana(BanNR);
It occurred because you tried to create a foreign key from tblDomare.PersNR to tblBana.BanNR but/and the values in tblDomare.PersNR didn't match with any of the values in tblBana.BanNR. You cannot create a relation which violates referential integrity.
This query was very useful for me. It shows all values that don't have any matches
select FK_column from FK_table
WHERE FK_column NOT IN
(SELECT PK_column from PK_table)
Try this solution:
There is a data item in your table whose associated value doesn't exist in the table you want to use it as a primary key table.
Make your table empty or add the associated value to the second table.
It is possible to create the foreign key using ALTER TABLE tablename WITH NOCHECK ..., which will allow data that violates the foreign key.
"ALTER TABLE tablename WITH NOCHECK ..." option to add the FK -- This solution worked for me.
Remove all existing data from your tables and then make a relation between the tables.
Before You add Foreign key to the table, do the following
Make sure the table must empty or The column data should match.
Make sure it is not null.
If the table contains do not go to design and change, do it manually.
alter table Table 1 add foreign key (Column Name) references Table 2 (Column Name)
alter table Table 1 alter column Column Name attribute not null
I guess, a column value in a foreign key table should match with the column value of the primary key table. If we are trying to create a foreign key constraint between two tables where the value inside one column(going to be the foreign key) is different from the column value of the primary key table then it will throw the message.
So it is always recommended to insert only those values in the Foreign key column which are present in the Primary key table column.
For ex. If the Primary table column has values 1, 2, 3 and in Foreign key column the values inserted are different, then the query would not be executed as it expects the values to be between 1 & 3.
In very simple words your table already has data present in it and the table you are trying to create relationship with does have that Primary key set for the values that are already present.
Either delete all the values of the existing table.
Add all the values of foreign key reference in the new table.
Try DELETE the current datas from tblDomare.PersNR . Because the values in tblDomare.PersNR didn't match with any of the values in tblBana.BanNR.
When you define a Foreign Key in table B referencing the Primary Key of table A it means that when a value is in B, it must be in A. This is to prevent unconsistent modifications to the tables.
In your example, your tables contain:
tblDomare with PRIMARY KEY (PersNR):
PersNR |fNamn |eNamn |Erfarenhet
-----------|----------|-----------|----------
6811034679 |'Bengt' |'Carlberg' |10
7606091347 |'Josefin' |'Backman' |4
8508284163 |'Johanna' |'Backman' |1
---------------------------------------------
tblBana:
BanNR
-----
1
2
3
-----
This statement:
ALTER TABLE tblDomare
ADD FOREIGN KEY (PersNR)
REFERENCES tblBana(BanNR);
says that any line in tblDomare with key PersNR must have a correspondence in table tblBana on key BanNR. Your error is because you have lines inserted in tblDomare with no correspondence in tblBana.
2 solutions to fix your issue:
either add lines in tblBana with BanNR in (6811034679, 7606091347, 8508284163)
or remove all lines in tblDomare that have no correspondence in tblBana (but your table would be empty)
General advice: you should have the Foreign Key constraint before populating the tables. Foreign keys are here to prevent the user of the table from filling the tables with inconsistencies.
i had this error too
as Smutje reffered make sure that you have not a value in foreign key column of your base foreign key table that is not in your reference table i.e(every value in your base foreign key table(value of a column that is foreign key) must also be in your reference table column)
its good to empty your base foreign key table first then set foreign keys
the data you have entered a table(tbldomare) aren't match a data you have assigned primary key table. write between tbldomare and add this word (with nocheck) then execute your code.
for example you entered a table tbldomar this data
INSERT INTO tblDomare (PersNR,fNamn,eNamn,Erfarenhet)
Values (6811034679,'Bengt','Carlberg',10);
and you assigned a foreign key table to accept only 1,2,3.
you have two solutions one is delete the data you have entered a table then execute the code. another is write this word (with nocheck) put it between your table name and add
like this
ALTER TABLE tblDomare with nocheck
ADD FOREIGN KEY (PersNR)
REFERENCES tblBana(BanNR);
Smutje is correct and Chad HedgeCock offered a great layman's example.
Id like to build on Chad's example by offering a way to find/delete those records.
We will use Customer as the Parent and Order as the child. CustomerId is the common field.
select * from Order Child
left join Customer Parent on Child.CustomerId = Parent.CustomerId
where Parent.CustomerId is null
if you are reading this thread... you will get results. These are orphaned children. select * from Order Child
left join Customer Parent on Child.CustomerId = Parent.CustomerId
where Parent.CustomerId is null Note the row count in the bottom right.
Go verify w/ whomever you need to that you are going to delete these rows!
begin tran
delete Order
from Order Child
left join Customer Parent on Child.CustomerId = Parent.CustomerId
where Parent.CustomerId is null
Run the first bit.
Check that row count = what you expected
commit the tran
commit tran
Be careful. Someone's sloppy programming got you into this mess. Make sure you understand the why before you delete the orphans. Maybe the parent needs to be restored.
From our end, this is the scenario:
We have an existing table in the database with records.
Then I introduces a NOT nullable foreign key
After executing the update i got this error.
How did i solve you ask?
SOLUTION: I just removed all the records of the table, then tried to update the database and it was successful.
This happens to me, since I am designing my database, I notice that I change my seed on my main table, now the relational table has no foreign key on the main table.
So I need to truncate both tables, and it now works!
You should see if your tables has any data on the rows. If "yes" then you should truncate the table(s) or else you can make them to have the same number of data at tblDomare.PersNR to tblBana.BanNR and vise-verse.
In my scenario, using EF, upon trying to create this new Foreign Key on existing data, I was wrongly trying to populate the data (make the links) AFTER creating the foreign key.
The fix is to populate your data before creating the foreign key since it checks all of them to see if the links are indeed valid. So it couldn't possibly work if you haven't populated it yet.
I encounter some issue in my project.
In child table, there isn't any record Id equals 1 and 11
I inserted DEAL_ITEM_THIRD_PARTY_PO table which Id equals 1 and 11 then I can create FK
Please first delete data from that table and then run the migration again. You will get success
I had the same problem.
My issue was having nullable: true in column (migration file):
AddColumn("dbo.table", "column", c => c.Int(nullable: true));
Possible Solutions:
Change nullable 'false' to 'true'. (Not Recommended)
Change property type from int to int? (Recommended)
And if required, change this later after adding column > then missing field data in previous records
If you've changed an existing property from nullable to non-nullable:
3) Fill the column data in database records
A foreign key constraint in a child table must have a parent table with a primary key. The primary key must be unique. The foreign key value must match a value in the patent table primary key
When you alter table column from nullable to not nullable column where this column is foreign key, you must :
Firstly, initialize this column with value (because it is foreign
key not nullable).
After that you can alter your table column normally.
Please try below query:
CREATE TABLE tblBana
(BanNR VARCHAR (15) NOT NULL PRIMARY KEY,
);
CREATE TABLE tblDomare
(PersNR VARCHAR (15) NOT NULL PRIMARY KEY,
fNamn VARCHAR (15) NOT NULL,
eNamn VARCHAR (20) NOT NULL,
Erfarenhet VARCHAR (5),
FK_tblBana_Id VARCHAR (15) references tblBana (BanNR)
);
INSERT INTO tblBana (BanNR)
Values (3);
INSERT INTO tblDomare (PersNR,fNamn,eNamn,Erfarenhet,FK_tblBana_Id)
Values (8508284173,'Johanna','Backman',1,3);
or you can use this
SELECT fk_id FROM dbo.tableA
Except
SELECT fk_id From dbo.tableB
and just FYI, in case you do all of your data reference checks and find no bad data...apparently it is not possible to create a foreign key constraint between two tables and fields where those fields are the primary key in both tables! Do not ask me how I know this.
How to change the type of a column in a SQLite table?
I've got:
CREATE TABLE table(
id INTEGER,
salt TEXT NOT NULL UNIQUE,
step INT,
insert_date TIMESTAMP
);
I'd like to change salt's type to just TEXT and id's type to INTEGER PRIMARY KEY.
Below is an excerpt from the SQLite manual discussing the ALTER TABLE command (see URL: SQLite Alter Table):
SQLite supports a limited subset of
ALTER TABLE. The ALTER TABLE command
in SQLite allows the user to rename a
table or to add a new column to an
existing table. It is not possible to
rename a colum, remove a column, or
add or remove constraints from a
table.
As the manual states, it is not possible to modify a column's type or constraints, such as converting NULL to NOT NULL. However, there is a work around by
copying the old table to a temporary table,
creating a new table defined as desired, and
copying the data from the temporary table to the new table.
To give credit where credit is due, I learned this from the discussion on Issue #1 of hakanw's django-email-usernames project on bitbucket.org.
CREATE TABLE test_table(
id INTEGER,
salt TEXT NOT NULL UNIQUE,
step INT,
insert_date TIMESTAMP
);
ALTER TABLE test_table RENAME TO test_table_temp;
CREATE TABLE test_table(
id INTEGER PRIMARY KEY,
salt TEXT,
step INT,
insert_date TIMESTAMP
);
INSERT INTO test_table SELECT * FROM test_table_temp;
DROP TABLE test_table_temp;
Notes
I used the table name test_table since SQLite will generate an error if you try to name a table as table.
The INSERT INTO command will fail if your data does not conform to the new table constraints. For instance, if the original test_table contains two id fields with the same integer, you will receive an "SQL error: PRIMARY KEY must be unique" when you execute the "INSERT INTO test_table SELECT * FROM test_table_temp;" command.
For all testing, I used SQLite version 3.4.0 as included as part of Python 2.6.2 running on my 13" Unibody MacBook with Mac OS X 10.5.7.
Since RDBMS is not specified, these are DB2 queries:
Make ID as primary key:
ALTER TABLE table
ADD CONSTRAINT pk_id
PRIMARY KEY (id)
Make salt as not UNIQUE:
ALTER TABLE table
DROP UNIQUE <salt-unique-constraint-name>
Make salt nullable:
ALTER TABLE table
ALTER COLUMN salt DROP NOT NULL
You will need to do a reorg after drop not null. This is to be done from the command prompt.
reorg table <tableName>
In this case you can make salt to nullable and remove unique constraint. Also If id column does not contain any null or duplicate values you can safely make it primary key using sql server management studio. below is the screen shot. hope it makes it clearer:
alt text http://img265.imageshack.us/img265/7418/91573473.png
or use following sql:
alter table <TableName> modify salt text null
alter table <TableName> drop constraint <Unique Constraint Name>
alter table <TableName> modify id int not null
alter table <TableName> add constraint pk<Table>d primary key (id)