I am trying to change the primary key of one of my tables from a simple to a composite key, where the composite should be composed of the old pk column and a newly created one.
I followed along this answer from a very similar question: https://stackoverflow.com/a/27832197/1948454
It almost works, except that there is no value set in the dependant table for the new column.
Here's the situation:
Suppose I have a table for a catalog, and a table for catalog entries. Before:
-- DDL Catalog
CREATE TABLE public.Catalog (
name_ VARCHAR(255) NOT NULL,
foo_ VARCHAR(255) NULL,
CONSTRAINT Catalog_pkey PRIMARY KEY (name_)
);
-- DDL CatalogEntry
CREATE TABLE public.CatalogEntry (
pricekey_ VARCHAR(255) NOT NULL,
pricekeyroot_ VARCHAR(255) NOT NULL,
catalog_name_ VARCHAR(255) NULL,
bar_ VARCHAR(255) NULL,
CONSTRAINT CatalogEntry_pkey PRIMARY KEY (pricekey_, pricekeyroot_)
);
-- public.CatalogEntry FOREIGN KEYs
ALTER TABLE public.CatalogEntry ADD CONSTRAINT CatalogEntry_catalog_name__fkey FOREIGN KEY (catalog_name_) REFERENCES Catalog(name_) ON DELETE CASCADE;
So CatalogEntry.catalog_name references to Catalog.name_.
Now I need to add another column version_ to the Catalog table, indicating a version of some catalog. This means I will have to create a new composite pk composed of name_ and version_. Here's my script:
-- UPDATE script
-- add the new version column and set all values to default of 1
ALTER TABLE Catalog ADD version_ INTEGER;
UPDATE Catalog SET version_ = 1;
ALTER TABLE Catalog ALTER column version_ SET not null;
-- update primary key and foreign key
BEGIN;
-- first, drop fkey constraint on CatalogEntry
ALTER TABLE CatalogEntry DROP CONSTRAINT CatalogEntry_catalog_name__fkey;
-- then, update Catalog primary key
ALTER TABLE Catalog DROP CONSTRAINT Catalog_pkey,
ADD CONSTRAINT Catalog_uni_name UNIQUE (name_),
ADD PRIMARY KEY (name_, version_);
-- now add new foreign key again to CatalogEntry
ALTER TABLE CatalogEntry ADD catalog_version_ INTEGER;
ALTER TABLE CatalogEntry
ADD CONSTRAINT CatalogEntry_catalog_name__catalog__fkey FOREIGN KEY (catalog_name_, catalog_version_)
references Catalog(name_, version_ ) ON DELETE CASCADE;
COMMIT;
-- finally, remove unique constraint on name since it is not needed anymore
ALTER TABLE Catalog DROP CONSTRAINT Catalog_uni_name;
After performing these steps, the primary and foreign key appear to be set correctly - but the value of CatalogEntry.catalog_version_ is null. The corresponding value of Catalog.version_ is set correctly to 1.
Where is my mistake? Do I also have to set CatalogEntry.catalog_version_ manually to 1? I would have assumed that it would be set automatically.
The value of CatalogEntry.catalog_version_ doesn't magically get set just because you define a foreign key constraint.
What effectively happened is that no row in CatalogEntry references a row in Catalog. The reason is that the default for foreign key constraints is MATCH SIMPLE, see the documentation:
MATCH SIMPLE allows any of the foreign key columns to be null; if any of them are null, the row is not required to have a match in the referenced table.
You should create the foreign key constraint as MATCH FULL so that either all or none of the columns must be NULL. Then you would have received an error creating the foreign key.
Solution: update CatalogEntry and set the column to 1 there as well, then define the foreign key with MATCH FULL.
Related
i want to add to a primary key in one table a references to the primary key of another table.
my code:
CREATE TABLE[payment]
(ID int Primary key)
CREATE TABLE [tab]
(ID int Primary key references tab2(ID))
Alter Table payment
alter column ID
ADD constraint fk_payment
references tab(ID)
i get the error that the syntax near constraint is wrong, but i don't know what to change
because of the not changeable order of the table Alter table is the only option. to reference from one table to the other doesn't work cause I've references from that table to another one already.
i need two one-to-one-relations from one table to another
If you want to add a FK constraint, just use this code:
ALTER TABLE dbo.payment
ADD CONSTRAINT fk_payment
FOREIGN KEY(ID) REFERENCES dbo.tab(ID)
You don't need to alter the column or table - just add the constraint
CREATE TABLE CUSTOMER
(
CNUM VARCHAR(25) NOT NULL,
CNAME VARCHAR(75) NOT NULL,
CTYPE VARCHAR(20) NOT NULL,
CONSTRAINT CUSTOMER_PK PRIMARY KEY(CNUM),
CONSTRAINT CHECK_CTYPE CHECK(CTYPE IN('INDIVIDUAL', 'INSTITUTION'))
);
CREATE TABLE CREDIT_TERM
(
CREDITSTATUS VARCHAR(20) NOT NULL,
STARTDATE DATE NOT NULL,
ENDDATE DATE NOT NULL,
CONSTRAINT CREDIT_TERM_PK PRIMARY KEY(CREDITSTATUS)
);
insert into CREDIT_TERM values('ONE-MONTH','15-05-2015','15-06-2015');
insert into CREDIT_TERM values('TWO-MONTH','15-05-2015','15-06-2015');
insert into CREDIT_TERM values('THREE-MONTH','15-05-2015','15-06-2015');
ALTER TABLE CUSTOMER
ADD CONSTRAINT CUSTOMER_FK_CREDITSTATUS
FOREIGN KEY(CREDITSTATUS) REFERENCES CREDIT_TERM(CREDITSTATUS);
I am trying to add a foreign key constraint, but I don't understand why I get this error:
ERROR at last line :
ORA-00904: "CREDITSTATUS": invalid identifier
As I noted in the comments, your customer table does not have a creditstatus column. You'd first have to add it:
ALTER TABLE customer ADD creditstatus VARCHAR2(20);
And then make it a foreign key, with the statement you already have.
You're trying to add a foreign key constraint for a foreign key named CREDITSTATUS on the CUSTOMER table. However, the CUSTOMER table doesn't have a foreign key for CREDITSTATUS.
You'll have to create a foreign key in CUSTOMER for CREDITSTATUS, then rerun the last line to add the constraint.
EDIT
Use ALTER TABLE to add the column to CUSTOMER:
ALTER TABLE CUSTOMER ADD CREDITSTATUS VARCHAR(20);
Docs:
http://www.techonthenet.com/oracle/tables/alter_table.php
You can add the column and the foreign key constraint in one statement:
alter table customer add (
creditstatus varchar2(20) constraint customer_fk_creditstatus references credit_term
);
A few notes. First, I enclosed the column definition in parentheses. It may work without them, but the official syntax seems to require them. http://docs.oracle.com/cd/B19306_01/server.102/b14200/statements_3001.htm#i2103924
Second, in an in-line constraint (defined at the column level, not at the table level), you may not use the words FOREIGN KEY. The word REFERENCES already identifies the constraint type. Third, if you reference the PRIMARY KEY of the referenced table, you are not required to (but you may if you wish) name the referenced column in the referenced table. If you don't name the column, the PRIMARY KEY of the referenced table will be used by default - which is what you want anyway, in the vast majority of cases.
I have not seen any clear, concise examples of this anywhere online.
With an existing table, how do I add a foreign key which references this table? For example:
CREATE TABLE dbo.Projects(
ProjectsID INT IDENTITY(1,1) PRIMARY KEY,
Name varchar(50)
);
How would I write a command to add a foreign key which references the same table? Can I do this in a single SQL command?
I'll show you several equivalent ways of declaring such a foreign key constraint. (This answer is intentionally repetitive to help you recognise the simple patterns for declaring constraints.)
Example: This is what we would like to end up with:
Case 1: The column holding the foreign keys already exists, but the foreign key relationship has not been declared / is not enforced yet:
In that case, run this statement:
ALTER TABLE Employee
ADD FOREIGN KEY (ManagerId) REFERENCES Employee (Id);
Case 2: The table exists, but it does not yet have the foreign key column:
ALTER TABLE Employee
ADD ManagerId INT, -- add the column; everything else is the same as with case 1
FOREIGN KEY (ManagerId) REFERENCES Employee (Id);
or more succinctly:
ALTER TABLE Employee
ADD ManagerId INT REFERENCES Employee (Id);
Case 3: The table does not exist yet.
CREATE TABLE Employee -- create the table; everything else is the same as with case 1
(
Id INT NOT NULL PRIMARY KEY,
ManagerId INT
);
ALTER TABLE Employee
ADD FOREIGN KEY (ManagerId) REFERENCES Employee (Id);
or, declare the constraint inline, as part of the table creation:
CREATE TABLE Employee
(
Id INT NOT NULL PRIMARY KEY,
ManagerId INT,
FOREIGN KEY (ManagerId) REFERENCES Employee (Id)
);
or even more succinctly:
CREATE TABLE Employee
(
Id INT NOT NULL PRIMARY KEY,
ManagerId INT REFERENCES Employee (Id)
);
P.S. regarding constraint naming: Up until the previous revision of this answer, the more verbose SQL examples contained CONSTRAINT <ConstraintName> clauses for giving unique names to the foreign key constraints. After a comment by #ypercube I've decided to drop these clauses from the examples, for two reasons: Naming a constraint is an orthogonal issue to (i.e. independent from) putting the constraint in place. And having the naming out of the way allows us to focus on the the actual adding of the constraints.
In short, in order to name a constraint, precede any mention of e.g. PRIMARY KEY, REFERENCES, or FOREIGN KEY with CONSTRAINT <ConstraintName>. The way I name foreign key constraints is <TableName>_FK_<ColumnName>. I name primary key constraints in the same way, only with PK instead of FK. (Natural and other alternate keys would get the name prefix AK.)
You can add the column and constraint in one operation
ALTER TABLE dbo.Projects ADD
parentId INT NULL,
CONSTRAINT FK FOREIGN KEY(parentid) REFERENCES dbo.Projects
Optionally you could specify the PK column in brackets after the referenced table name but it is not needed here.
If the table already exists: Assuming you don't already have a column to store this data. If you do then skip this step.
ALTER TABLE [dbo].[project]
ADD [fkProjectsId] INT;
GO
ALTER TABLE [dbo].[projects]
ADD CONSTRAINT [FK_Projects_ProjectsId] FOREIGN KEY ([fkProjectsId]) REFERENCES [dbo].[Projects] ([ProjectsID])
GO
I am new to this website, i hope that i ask the question the right way
-- Create a Database table to represent the "FACT" entity.
CREATE TABLE FACT
(
Time_id DATE NOT NULL,
Area_id INTEGER NOT NULL,
Reported_crime_id INTEGER NOT NULL,
Crime_status VARCHAR(8) NOT NULL,
no_of_crime INTEGER NOT NULL,
Max_crime INTEGER NOT NULL,
Avg_crime INTEGER NOT NULL,
Min_crime INTEGER NOT NULL,
date_reported DATE NOT NULL,
-- Specify the PRIMARY KEY constraint for table "FACT".
-- This indicates which attribute(s) uniquely identify each row of data.
CONSTRAINT pk_fact PRIMARY KEY (Time_id, Area_id, Reported_crime_id,
Crime_status)
);
-- Create a Database table to represent the "Crime_Dim" entity.
CREATE TABLE Crime_Dim
(
REPORTED_CRIME_ID INTEGER NOT NULL,
CRIME_TYPE_Desc VARCHAR(50),
DATE_REPORTED DATE NOT NULL,
Crime_type_id INTEGER NOT NULL,
-- Specify the PRIMARY KEY constraint for table "Crime_Dim".
-- This indicates which attribute(s) uniquely identify each row of data.
CONSTRAINT pk_crime_dim PRIMARY KEY (REPORTED_CRIME_ID)
);
-- Create a Database table to represent the "Location_Dim" entity.
CREATE TABLE Location_Dim
(
AREA_ID INTEGER NOT NULL,
AREA_Name VARCHAR(30) NOT NULL,
Area_code INTEGER NOT NULL,
Force_id INTEGER NOT NULL,
-- Specify the PRIMARY KEY constraint for table "Location_Dim".
-- This indicates which attribute(s) uniquely identify each row of data.
CONSTRAINT pk_location_dim PRIMARY KEY (AREA_ID)
);
-- Create a Database table to represent the "Time_Dim" entity.
CREATE TABLE Time_Dim
(
Time_id INTEGER NOT NULL,
day_id INTEGER NOT NULL,
Month_id INTEGER NOT NULL,
Year INTEGER,
-- Specify the PRIMARY KEY constraint for table "Time_Dim".
-- This indicates which attribute(s) uniquely identify each row of data.
CONSTRAINT pk_time_dim PRIMARY KEY (Time_id)
);
-- Create a Database table to represent the "Reported_crime_dim" entity.
CREATE TABLE Reported_crime_dim
(
Crime_status VARCHAR(20) NOT NULL,
Date_reported DATE NOT NULL,
-- Specify the PRIMARY KEY constraint for table "Reported_crime_dim".
-- This indicates which attribute(s) uniquely identify each row of data.
CONSTRAINT pk_reported_crime_dim PRIMARY KEY (Crime_status)
);
-- i.e. tables may be referenced before they have been created. This method is therefore safer.
-- Alter table to add new constraints required to implement the "FACT_Time_Dim" relationship
-- This constraint ensures that the foreign key of table "FACT"
-- correctly references the primary key of table "Time_Dim"
ALTER TABLE FACT
ADD CONSTRAINT fk1_fact_to_time_dim FOREIGN KEY(Time_id) REFERENCES Time_Dim(
Time_id) ON DELETE RESTRICT ON UPDATE RESTRICT;
-- Alter table to add new constraints required to implement the "FACT_Location_Dim" relationship
-- This constraint ensures that the foreign key of table "FACT"
-- correctly references the primary key of table "Location_Dim"
ALTER TABLE FACT
ADD CONSTRAINT fk2_fact_to_location_dim FOREIGN KEY(AREA_ID) REFERENCES
Location_Dim(AREA_ID) ON DELETE RESTRICT ON UPDATE RESTRICT;
-- Alter table to add new constraints required to implement the "FACT_Crime_Dim" relationship
-- This constraint ensures that the foreign key of table "FACT"
-- correctly references the primary key of table "Crime_Dim"
ALTER TABLE FACT
ADD CONSTRAINT fk3_fact_to_crime_dim FOREIGN KEY(REPORTED_CRIME_ID) REFERENCES
Crime_Dim(REPORTED_CRIME_ID) ON DELETE RESTRICT ON UPDATE RESTRICT;
-- Alter table to add new constraints required to implement the "FACT_Reported_crime_dim" relationship
-- This constraint ensures that the foreign key of table "FACT"
-- correctly references the primary key of table "Reported_crime_dim"
ALTER TABLE FACT
ADD CONSTRAINT fk4_fact_to_reported_crime_dim FOREIGN KEY(Crime_status)
REFERENCES Reported_crime_dim(Crime_status) ON DELETE RESTRICT ON UPDATE
RESTRICT;
--------------------------------------------------------------
-- End of DDL file auto-generation
--------------------------------------------------------------
Could someone help me in correcting the errors in the sql code above? when i run the code as mentioned at the last few codes i need to create constraint to prevent Foreign keys in the Fact table and relate them back to their original table if i have got this right...
could someone correct the code and let me know plz
Following this answer, you have to remove ON DELETE RESTRICT and ON UPDATE RESTRICT.
There's no such option in Oracle.
I have a table in Oracle which has following schema:
City_ID Name State Country BuildTime Time
When I declared the table my primary key was both City_ID and the BuildTime, but now I want to change the primary key to three columns:
City_ID BuildTime Time
How can I change the primary key?
Assuming that your table name is city and your existing Primary Key is pk_city, you should be able to do the following:
ALTER TABLE city
DROP CONSTRAINT pk_city;
ALTER TABLE city
ADD CONSTRAINT pk_city PRIMARY KEY (city_id, buildtime, time);
Make sure that there are no records where time is NULL, otherwise you won't be able to re-create the constraint.
You will need to drop and re-create the primary key like this:
alter table my_table drop constraint my_pk;
alter table my_table add constraint my_pk primary key (city_id, buildtime, time);
However, if there are other tables with foreign keys that reference this primary key, then you will need to drop those first, do the above, and then re-create the foreign keys with the new column list.
An alternative syntax to drop the existing primary key (e.g. if you don't know the constraint name):
alter table my_table drop primary key;
Sometimes when we do these steps:
alter table my_table drop constraint my_pk;
alter table my_table add constraint my_pk primary key (city_id, buildtime, time);
The last statement fails with
ORA-00955 "name is already used by an existing object"
Oracle usually creates an unique index with the same name my_pk. In such a case you can drop the unique index or rename it based on whether the constraint is still relevant.
You can combine the dropping of primary key constraint and unique index into a single sql statement:
alter table my_table drop constraint my_pk drop index;
check this:
ORA-00955 "name is already used by an existing object"