I have a question regarding to primary key for Oracle Table with Period.
I have created two tables like following:
create table el_temporal_try( -- Parent Table
id number(10) not null,
ColumnA varchar(10),
constraint el_temporal_try_pk primary key (id),
period for valid_period
);
create table el_temporal_try_son( -- Son Table
id number(10) not null,
ColumnA varchar(10),
parent_id number(10),
constraint el_temporal_try_FY foreign key (parent_id) references el_temporal_try(id),
period for valid_period
);
This script gone through successfully. However I have problem with inserting data:
I have executed following two insert statements into the parent table:
1st: statement
insert into el_temporal_try
(id, columnA,valid_period_start, valid_period_end)
values
(1,'A',sysdate - 10, sysdate - 9);
Result:
1 row inserted.
2nd: statement
insert into el_temporal_try
(id, columnA,valid_period_start, valid_period_end)
values
(1,'B',sysdate - 8, sysdate - 7);
Result
ORA-00001: unique constraint (PBSVW.EL_TEMPORAL_TRY_PK) violated
I understand it is because of the "ID" column. However, my issues because this two rows are for a different period, should it be allowed?
I was intended to use this period for feature to capture the change history of a record as an alternative to flashback. However, does it means that I should not use primary key at this situation?
Thanks in advance!
The problem is related to the id column like you said. it's not possible to add the registry because the primary key is unique, then your second insert statement references the same ID from the first. You need to change the ID always you insert a line.
On Oracle 12c, you can use the identity like this link.
https://www.oracletutorial.com/oracle-basics/oracle-identity-column/
in another version, you can use sequence and trigger to do this.
https://chartio.com/resources/tutorials/how-to-define-an-auto-increment-primary-key-in-oracle/
Thanks for everyone's help on this. This most likely means I cannot use Primary Key/Foreign Key to maintain the referential integrity between the parent and son for my situation within a particular timestamp, but I have to go for something else.
Thanks a lot!
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.
We are using Oracle database in our projects. And we define as much as constraints that can be applied to database, (including primary, unique, check and foreign key constraints).
It seems that defining constraints DEFERRABLE allows us to DEFER them when it is required, so why shall any constraint be defined as NOT DEFERRABLE?
Why databases such as Oracle have NOT DEFERRABLE as default case?
Are there any pros for defining a constraint NOT DEFERRABLE?
The major use case for deferrable constraints is that you don't need to worry about the order in which you do DML statements for multiple tables that have a foreign key relationship.
Consider the following example:
create table parent
(
id integer not null primary key
);
create table child
(
id integer not null primary key,
parent_id integer not null references parent
);
create table grand_child
(
id integer not null primary key,
child_id integer not null references child
);
If the constraints are immediate you have to insert (or delete) rows (that reference each other) in the proper sequence, which can e.g. be a problem when bulk loading data. If the constraints are deferred you can insert/delete the rows in any sequence as long as everything is fine when you commit your transaction.
So with a deferrable constraint (which the above example does not create!) you could the following:
insert into grand_child values (1,1);
insert into child values (1,1);
insert into parent values (1);
commit;
That would not be possible if the constraints were immediate.
A special case of the above example are cyclic references:
create table one
(
id integer not null primary key,
id_two integer not null
);
create table two
(
id integer not null primary key
id_one integer not null
);
alter table one add constraint fk_one_two (id_two) references two(id);
alter table two add constraint fk_two_one (id_one) references one(id);
Without declaring the constraints as deferrable you will not be able to insert data into those tables at all.
The workaround for DBMS that do not support deferrable constraints would be to make the fk columns nullable. And then insert null values first:
insert into one values (1, null);
insert into two values (1, 1);
update one
set id_two = 1
where id = 1;
With a deferrable constraint you don't need the additional update statement.
(The design using a cyclic reference is however very often questionable!)
I don't use deferrable constraints where often, but I wouldn't want to live without them.
One drawback of deferrable constraints is error checking though. You don't know until you commit if your data is correct. That makes finding out what went wrong a bit more complicated. If you get the error when doing the insert (or delete or update) you immediately know which values caused the error.
I have an sqlite database structured as follows:
CREATE TABLE IF NOT EXISTS Patient
( PatientId INTEGER PRIMARY KEY AUTOINCREMENT );
CREATE TABLE IF NOT EXISTS Event
(
PatientId INTEGER REFERENCES Patient( PatientId ),
DateTime TEXT,
EventTypeCode TEXT,
PRIMARY KEY( PatientId, DateTime, EventTypeCode )
);
CREATE TABLE IF NOT EXISTS Reading
(
PatientId INTEGER REFERENCES Patient( PatientId ),
DateTime TEXT REFERENCES Event (DateTime),
EventTypeCode TEXT REFERENCES Event (EventTypeCode),
Value REAL,
PRIMARY KEY( PatientId, DateTime, EventTypeCode )
);
I insert a Patient with Id #1
then I run:
INSERT INTO Event (PatientId, DateTime, EventTypeCode) VALUES (1, '2011-01-23 19:26:59', 'R')
which works
then I run:
INSERT INTO Reading (PatientId, DateTime, EventTypeCode, Value) VALUES (1, '2011-01-23 19:26:59', 'R', 7.9)
and it gives me a foreign key mismatch. Patient Id is '1' in all cases, and the datetime and typecodes match in the 2nd and 3rd queries. I do not understand what is mismatching, but I'm a bit new to actually defining foreign keys and i do not know what I am doing wrong.
I'm not familiar with SQLite but a little Google'ing turned up this. The documentation says
If the database schema contains
foreign key errors that require
looking at more than one table
definition to identify, then those
errors are not detected when the
tables are created. Instead, such
errors prevent the application from
preparing SQL statements that modify
the content of the child or parent
tables in ways that use the foreign
keys. Errors reported when content is
changed are "DML errors" and errors
reported when the schema is changed
are "DDL errors". So, in other words,
misconfigured foreign key constraints
that require looking at both the child
and parent are DML errors. The English
language error message for foreign key
DML errors is usually "foreign key
mismatch" but can also be "no such
table" if the parent table does not
exist. Foreign key DML errors are may
be
reported if:
The parent table does not exist, or
The parent key columns named in the foreign key constraint do not exist,
or
The parent key columns named in the foreign key constraint are not the
primary key of the parent table and
are not subject to a unique constraint
using collating sequence specified in
the CREATE TABLE, or
The child table references the primary key of the parent without
specifying the primary key columns and
the number of primary key columns in
the parent do not match the number of
child key columns.
I suspect you might be running into #3 in that list.
Also, while other DBs might support using a non-unique index as a foreign key reference, (see answers here), it's a bad design choice in my opinion. I would restructure so that either
Reading.PatientId references Event.PatientId so that the complete composite key from Event is referenced by Reading or,
Add an EventId auto-increment, primary key to the Event table and use that as the foreign key in the Reading table (so that you only have EventId and Value under Reading and you can get the PatientId, DateTime, EventTypeCode out of Event).
I'd suggest #2 so that you can avoid the redundancy of PatientId, DateTime and EventTypeCode in both Event and Reading.