I have about 5000 records in a table in SQL Server 2008
I need to add a primary key. I don't care what it is, maybe an autonumber would be best?
How do I add a primary key to every record ?
I also would like this primary key to be generated automatically when I add new rows!
Try this:
ALTER TABLE myTable ADD id INT IDENTITY
CONSTRAINT id _pk PRIMARY KEY;
Related
In my table I have a self increment identity key but its not primary. If alter this key to make it primary also, in an existing table will it cause any problems?
No its pretty safe. Use:
alter table create primary key (column_name)
I added a constraint primary key to my table and the query ran successfully. The dilemma I am facing is I cannot locate the primary key column in my table.
ALTER TABLE salesdata
ADD CONSTRAINT pk_salesdata PRIMARY KEY( "Address_of_New_Home","Sq_Ft","Build_Spec", "Realtor_Sale","Can","Actual_Sale_Date")
When I do:
select * from salesdata
It shows all the columns from before and no primary key column (pk_salesdata).
And even more baffling is when:
select pk_salesdata from salesdata
Database shows:
ERROR: column "pk_salesdata" does not exist
I want to add primary key column to the table. I humbly request assistance of databasers.
You create PRIMARY KEY, but...
you create composed primary key from columns "Address_of_New_Home", "Sq_Ft", "Build_Spec", "Realtor_Sale", "Can", "Actual_Sale_Date" - it is not good idea
your primary key have an alias name pk_salesdata, but it's only constraint name
you didn't create new column
If you would like new synthetic primary key column you have to use command:
ALTER TABLE salesdata ADD COLUMN mynewautoincrementid SERIAL PRIMARY KEY;
Primary Kay it's constraint in table when you add a primary key to any column you can select column name to show data
It looks like you've wrapped the columns you want to include in your primary keys in double quotes. That's not how this command works. Drop the quotes re-run the command and see what happens.
ALTER TABLE salesdata
ADD CONSTRAINT pk_salesdata PRIMARY KEY( Address_of_New_Home,Sq_Ft,Build_Spec, Realtor_Sale,Can,Actual_Sale_Date)
It might be easier to add a primary index through the SQL GUI.
Here's the MS documentation page for creating a primary key.
https://msdn.microsoft.com/en-us/library/ms189039.aspx
Note: Since your adding a primary key don't expect it to be available as a column.
What is the difference between using or not using the CONSTRAINT keyword when working with Foreign Keys on SQL Server?
I noticed that apparently both worked the same in this specific case, without CONSTRAINT:
CREATE TABLE ClientsPhones
(
ClientPhone varchar(10) NOT NULL,
ClientID smallint NOT NULL,
PRIMARY KEY (ClientPhone),
FOREIGN KEY (ClientID) REFERENCES Clients(ClientID)
);
And with CONSTRAINT:
CREATE TABLE ClientsPhones
(
ClientPhone varchar(10) NOT NULL,
ClientID smallint NOT NULL,
PRIMARY KEY (ClientPhone),
CONSTRAINT fk_ClientID
FOREIGN KEY (ClientID) REFERENCES Clients(ClientID)
);
Both didn't let me add records to the table unless the ClientID already existed on the Clients table, and the same ClientID and ClientPhone weren't already on the ClientsPhones table.
Is there any real difference between the two besides the fact that I'm able to name the constraint?
If you don't create constraint.it will automatically create own constraint name
the foreign key index name is generated using the name of the referencing foreign key column Automatically.
So there is no way to see difference of using and not using Constraint keyword. by default constraint name will be defined.
I did some research and don't believe Hell Boy's answer was as clear as it could be and had some misinformation.
Every constraint you add to a database has a name set by default. This includes PRIMARY KEY, FOREIGN KEY, DEFAULT, NOT NULL. It isn't necessarily the name of the column(s) used.
You can imagine that when you don't use the CONSTRAINT keyword SQL Server puts it there as well as generates a name for you.
If you want to remove or change a constrain you would either have to delete the entire table and recreate it with the correct constraints or you can reference the constraint by name and then alter it somewhat like a column using the ALTER keyword. This can be useful for when you need to delete a table with a foreign key. If you name the foreign key constraint you can delete it and then the table instead of having to delete the table the foreign key points to.
I have to add a auto_Increment primary key column to the table. I used this script to create but its doing fine. but one thing is thtat I have alredy have a primary key in that table. so its throwing an error.
how to remove alredy existing primary and making a new auto_increamtn column has a primary key.
ALTER TABLE ABCD ADD ABCD_Id int NOT NULL IDENTITY (1,1) PRIMARY KEY
thanks
You need to drop the PRIMARY key constraint first, something like
ALTER TABLE DROP CONSTRAINT PK_Table_Col
Is it possible to auto increment a column in SQL Server WITHOUT it being a primary key?
If yes how can this be done.
Thanks
Yes. There is no requirement that IDENTITY columns be made a primary key.
CREATE TABLE T
(
X INT PRIMARY KEY,
Y INT IDENTITY(1,1)
)
Though I'm not sure when this would be useful. If you have a natural key that you want to use as the PK then you would probably want to put a unique constraint on the surrogate alternate key anyway.
For purposes of setting up FK relationships SQL Server doesn't care if the column(s) is the PK or not it just requires a unique index on it/them.
Declare the column with the IDENTITY keyword, and simply do not create a PRIMARY KEY constraint on it.