There are two tables - orders and a list of services. In the first there is a bool field that the order is approved, if it is true then you can’t insert / delete values in the second table. With the UPDATE of the first table and the DELETE of the second, it is clear.
INSERT make as
INSERT INTO b (a_id, b_value)
SELECT *
FROM (VALUES (1, 'AA1-BB1'),(1, 'AA1-BB2'),(1, 'AA1-BB3')) va
WHERE (SELECT NOT confirm FROM a WHERE a_id = 2);
https://dbfiddle.uk/?rdbms=postgres_12&fiddle=7b0086967c1c38b0c80ca5624ebe92e9
How to forbid to insert without triggers and stored procedures? Is it possible to compose somehow complex constraint or a foreign key for checking conditions at the DBMS level?
The most recent version of Postgres supports generated columns. So, you can do:
alter table b add confirm boolean generated always as (false) stored;
Then create a unique key in a:
alter table a add constraint unq_a_confirm_id unique (confirm, id);
And finally the foreign key relationship:
alter table b add constraint fk_b_a_id_confirm
foreign key (confirm, a_id) references a(confirm, id);
Now, only confirmed = false ids can be used. Note that this will prevent updates to a that would invalidate the foreign key constraint.
I have these Oracle tables:
CREATE TABLE AGENT(
ID INTEGER NOT NULL,
GROUP_ID NUMBER(38,0),
........
)
/
CREATE INDEX IX_RELATIONSHIP_AG_GROUP ON AGENT (GROUP_ID)
/
ALTER TABLE AGENT ADD CONSTRAINT AGENTID PRIMARY KEY (ID)
/
CREATE TABLE AGENT_CONFIG(
AGENT_CONFIG_ID INTEGER NOT NULL,
AGENT_ID INTEGER,
.......
)
/
CREATE INDEX IX_RELATIONSHIP16 ON AGENT_CONFIG (AGENT_ID)
/
ALTER TABLE AGENT_CONFIG ADD CONSTRAINT KEY17 PRIMARY KEY (AGENT_CONFIG_ID)
/
ALTER TABLE AGENT_CONFIG ADD CONSTRAINT RELATIONSHIP16 FOREIGN KEY (AGENT_ID) REFERENCES AGENT (ID)
/
I want to use the first table AGENT as main table to store data. Into the second table I want to store configuration about AGENT and use AGENT ID as unique ID.
But I have this problem: I insert successfully row into table AGENT. I need to also add empty row with the same ID into table AGENT_CONFIG and later update that row. How I can duplicate this ID value duplication? Probably with Oracle table trigger? Is three any other way like special relation between the tables?
I use this SQL Query for insert into AGENT table:
INSERT INTO AGENT ("ID, GROUP_ID, NAME.....) VALUES (AGENT_SEQ.nextval, ?, ......)
Is this correct query:
INSERT INTO AGENT (ID, GROUP_ID......) VALUES (AGENT_SEQ.nextval, ?.......)
RETURNING id INTO INSERT INTO AGENT_CONFIG (AGENT_SEQ.nextval, Agent_ID) VALUES (id)"
For this use currval pseudocolumn (as #Nicholas Krasnov specified) of the sequence that you are using after you use nextval for table "AGENT". Currval will duplicate the value that you used for table "AGENT".
So for example :
1. INSERT INTO AGENT (ID, GROUP_ID......) VALUES (AGENT_SEQ.nextval, .......)
2. INSERT INTO AGENT_CONFIG (AGENT_CONFIG_ID,AGENT_ID) VALUES (NULL,AGENT_SEQ.CURRVAL) ;
Link for Sequence Pseudocolumns --> https://docs.oracle.com/cd/B28359_01/server.111/b28286/pseudocolumns002.htm
To establish a 1:1 or 1:{1,n} relation is not that easy:
On every insert in the parent table you'd have to make sure an according insert in the child table is also made.
On every delete from the parent table you'd have to make sure to delete the according child records (usually via cascading delete or by mere foreign key constraints).
On every delete from the child table you'd have to make sure it's not the last one for its parent. (And in that case either forbid the delete or delete the parent with it.)
Forbid or react on updates to the IDs.
You can solve this by disabling (i.e. not granting) direct inserts and deletes (and maybe updates) on the table and provide PL/SQL functions to handle these instead.
If you are okay, however, with a 1:{0,1} or 1:{0,n} relation, then you can simply write the parent record and then look up its ID to write the child record(s).
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.
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.