I have a ValidationTable like
and OrderProcessing table like
I want to create foreign key constraint on OrderProcessing table on column OrderType that references first 3 rows of ValidationTable (of ValidationType = "orders"). Is this possible? I referred similar questions but those did not really help.
I don't believe it is possible to link a specific set of rows.
The constraint has to be for the whole column.
I am using SQL Server 2012 and need to add a column with a unique primary key. I am about to load several hundred thousand records BULK and just discovered repetition in the field I was going to use. Have seen SEQUENCE and GUID. Need some guidance on the best choice and how to go about setting this up so that the key field is populated during the bulk load.
When you create your table in which you want to insert information create an IDENTITY column. That will serve as an auto-populating column with a unique number for each record.
Here is a link that might help you.
If you have already created your table just change this query to what suits to your table name and run it in order to add the new column you requested.
ALTER TABLE mytable
ADD COLUMN unique_id IDENTITY (1,1)
Just a slight update on what’s already posted that includes details for adding primary key constraint
alter table database.schema.table_t
add ID_column int identity(1,1)
primary key (ID_column)
If you already set the primary key on this table just go and remove it before you execute this statement.
How do I auto increment the primary key in a SQL Server database table? I've had a look through the forum but can't see how to do this.
I've looked at the properties but can't see an option. I saw an answer where you go to the Identity specification property and set it to yes and set the Identity increment to 1, but that section is grayed out and I can't change the no to yes.
There must be a simple way to do this but I can't find it.
Make sure that the Key column's datatype is int and then setting identity manually, as image shows
Or just run this code
-- ID is the name of the [to be] identity column
ALTER TABLE [yourTable] DROP COLUMN ID
ALTER TABLE [yourTable] ADD ID INT IDENTITY(1,1)
the code will run, if ID is not the only column in the table
image reference fifo's
When you're creating the table, you can create an IDENTITY column as follows:
CREATE TABLE (
ID_column INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
...
);
The IDENTITY property will auto-increment the column up from number 1. (Note that the data type of the column has to be an integer.) If you want to add this to an existing column, use an ALTER TABLE command.
Edit:
Tested a bit, and I can't find a way to change the Identity properties via the Column Properties window for various tables. I guess if you want to make a column an identity column, you HAVE to use an ALTER TABLE command.
You have to expand the Identity section to expose increment and seed.
Edit: I assumed that you'd have an integer datatype, not char(10). Which is reasonable I'd say and valid when I posted this answer
Expand your database, expand your table right click on your table and select design from dropdown.
Now go Column properties below of it scroll down and find Identity Specification, expand it and you will find Is Identity make it Yes. Now choose Identity Increment right below of it give the value you want to increment in it.
CREATE TABLE Persons (
Personid int IDENTITY(1,1) PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int
);
The MS SQL Server uses the IDENTITY keyword to perform an auto-increment feature.
In the example above, the starting value for IDENTITY is 1, and it will increment by 1 for each new record.
Tip: To specify that the "Personid" column should start at value 10 and increment by 5, change it to IDENTITY(10,5).
To insert a new record into the "Persons" table, we will NOT have to specify a value for the "Personid" column (a unique value will be added automatically):
Perhaps I'm missing something but why doesn't this work with the SEQUENCE object? Is this not what you're looking for?
Example:
CREATE SCHEMA blah.
GO
CREATE SEQUENCE blah.blahsequence
START WITH 1
INCREMENT BY 1
NO CYCLE;
CREATE TABLE blah.de_blah_blah
(numbers bigint PRIMARY KEY NOT NULL
......etc
When referencing the squence in say an INSERT command just use:
NEXT VALUE FOR blah.blahsequence
More information and options for SEQUENCE
When you're using Data Type: int you can select the row which you want to get autoincremented and go to the column properties tag. There you can set the identity to 'yes'. The starting value for autoincrement can also be edited there. Hope I could help ;)
I had this issue where I had already created the table and could not change it without dropping the table so what I did was:
(Not sure when they implemented this but had it in SQL 2016)
Right click on the table in the Object Explorer:
Script Table as > DROP And CREATE To > New Query Editor Window
Then do the edit to the script said by Josien; scroll to the bottom where the CREATE TABLE is, find your Primary Key and append IDENTITY(1,1) to the end before the comma. Run script.
The DROP and CREATE script was also helpful for me because of this issue. (Which the generated script handles.)
You can use the keyword IDENTITY as the data type to the column along with PRIMARY KEY constraint when creating the table.
ex:
StudentNumber IDENTITY(1,1) PRIMARY KEY
In here the first '1' means the starting value and the second '1' is the incrementing value.
If the table is already populated it is not possible to change a column to IDENTITY column or convert it to non IDENTITY column. You would need to export all the data out then you can change column type to IDENTITY or vice versa and then import data back.
I know it is painful process but I believe there is no alternative except for using sequence as mentioned in this post.
Be carefull like if you want the ID elements to be contigius or not. As SQLSERVER ID can jump by 1000 .
Examle: before restart ID=11
after restart , you insert new row in the table, then the id will be 1012.
You could do the following: New Table Creation:
-- create new table with Column ID which is Primary Key and Auto Increment --
CREATE TABLE titles(
id INT NOT NULL IDENTITY(1,1) PRIMARY KEY, --Primary Key with Auto-Increment --
keyword VARCHAR(260),
status VARCHAR(10),
);
If you Table Already exists and need to make the changes to ID column to be auto-increment and Primary key, then see below:
ALTER TABLE table DROP COLUMN id; // drop the existing ID in the table
ALTER TABLE table ADD id int IDENTITY(1, 1) NOT NULL; // add new column ID with auto-increment
ALTER TABLE table ADD CONSTRAINT PK_ident_test PRIMARY KEY CLUSTERED (id); // make it primary key
We have a production table with 770 million rows and change. We want(/need?) to change the Primary ID column from int to bigint to allow for future growth (and to avoid the sudden stop when the 32bit integer space is exhausted)
Experiments in DEV have shown that this is not as simple as altering the column as we would need to drop the index and then re-create it. So far in DEV (which is a bit humbler than PROD) the dropping of the index has not finished after 1 and a half hours. This table is hit 24/7 and having it offline for such a long time is not an option.
Has anyone else had to deal with a similar situation? How did you get it done?
Are there alternatives?
Edit: Additional Info:
The Primary key is clustered.
You could attempt a staged approach.
Create a new bigint column
Create an insert trigger to keep new entries in sync with the 2 columns
Execute an update to populate all the empty values in the bigint column with the converted value
Change the primary index on the table from your old id column to the new one
Point any FK's and queries to use the new column
Change the new column to become your identity column and remove the insert trigger from #2
Delete the old ID column
You should end up spreading the pain out over these 7 steps instead of hitting it all at once.
Create a parallel table with the longer data type for new rows and UNION the results?
What I had to do was copy the data into a new table with the desired structure (primary/clustered key only, non-clustered/FK once complete). If you don't have the room, you could bcp out the data and back in. You may need an application outage to make this happen.
What doesn't work: alter table Orderhistory alter column ID bigint because of the primary key. Don't drop the key and alter column as you will just fill your log file and take much longer than copy/bcp.
Never use the SSMS tools designer to change a column property, it copies table into temp table then does a rename once done. Lookup the alter table alter column syntax and use it and possibly defrag once complete if you modified a column wider that sits in middle of table.
I'm having trouble figuring out how to create a foreign key constraint. My data model is fixed and out of my control, it looks like this:
CREATE TABLE Enquiry
(Enquiry_Ref INTEGER PRIMARY KEY CLUSTERED, Join_Ref INTEGER, EnquiryDate, EnquiryType...)
CREATE TABLE Contact
(Contact_Ref INTEGER PRIMARY KEY CLUSTERED, Surname, Forenames ....)
CREATE TABLE UniversalJoin
(Join_Ref INTEGER, Contact_Ref INTEGER, Rel_Type INTEGER)
Each Enquiry has exactly one Contact. The link between the two is the UniversalJoin table where
Enquiry.Join_Ref = UniversalJoin.Join_Ref AND
Rel_Type = 1 AND
UniversalJoin.Contact_Ref = Contact.Contact_Ref
The Rel_Type differs depending on what the source table is, so in the case of Enquiry, Rel_Type is 1 but for another table it would set to N.
My question is how do I create a foreign key constraint to enforce the integrity of this relationship? What I want to say, but can't, is:
CREATE TABLE Enquiry
...
CONSTRAINT FK_Foo
FOREIGN KEY (Join_Ref)
REFERENCES UniversalJoin (JoinRef WHERE Rel_Type=1)
You can't use conditional or filtered foreign keys in SQL Server
In these cases, you could have a multiple column FK between (JoinRef, Rel_Type) and set a check constraint on Rel_Type in UniversalJoin to make it 1.
However, I think you are trying to have a row with multiple parents which can't be done.
You might rather want to have a look at CHECK Constraints
CHECK constraints enforce domain
integrity by limiting the values that
are accepted by a column. They are
similar to FOREIGN KEY constraints in
that they control the values that are
put in a column. The difference is in
how they determine which values are
valid: FOREIGN KEY constraints obtain
the list of valid values from another
table, and CHECK constraints determine
the valid values from a logical
expression that is not based on data
in another column.
You could use a table trigger with INSERT and Update to layer the equivalent as a FK.
This way you are able to apply conditions i.e. if column value =1 check exists in table a if column value = 2 then check another table.