I have an SSMS table that has one column that is a pk and set to auto increment. In my code I need to create a row and then pull the value of the ID.
I don't want to set the id, it needs to auto generate. Is there a way to do this without adding a second column to add data into?
Just use the phrase "DEFAULT VALUES" in place of a field list and values specification:
INSERT INTO [TableName] DEFAULT VALUES;
Test with:
CREATE TABLE #Test
(
ID INT IDENTITY(1, 1) NOT NULL PRIMARY KEY
);
INSERT INTO #Test DEFAULT VALUES;
SELECT SCOPE_IDENTITY();
For more info on this, check out the MSDN page for INSERT and do a "find" (i.e. Control-F) in your browser for "default values".
Related
In SQL Server, I have created a Table with an ID column that I have made an IDENTITY COLUMN,
EmployeeID int NOT NULL IDENTITY(100,10) PRIMARY KEY
It is my understanding, when I use the IDENTITY feature, it auto increments the EmployeeID. What I don't know/not sure is:
Is that IDENTITY number created, unique?
Does SQL search the entire column in the table to confirm the number created does not already exist?
Can I override that auto increment number manually?
If I did manually override that number, would the number I enter be checked to make sure it is not a duplicate/existing ID number?
Thanks for any help provided.
Is that IDENTITY number created, unique?
Yes, Identity property is unique
Does SQL search the entire column in the table to confirm the number created does not already exist? \
It need not, what this property does is, just incrementing the old value
Can I override that auto increment number manually?
Yes, you can. You have to use SET IDENTITY_INSERT TABLENAME ON
If I did manually override that number, would the number I enter be checked to make sure it is not a duplicate/existing ID number?
No, that won't be taken care by SQL Server, you will have to ensure you have constraints to take care of this
Below is a simple demo to prove that
create table #temp
(
id int identity(1,1)
)
insert into #temp
default values
go 3
select * from #temp--now id column has 3
set identity_insert #temp on
insert into #temp (id)
values(4)
set identity_insert #temp off
select * from #temp--now id column has 4
insert into #temp
default values
go
select * from #temp--now id column has 5,next value from the last highest
Updating info from comments:
Identity column will allow gaps once you reseed them,also you can't update them
I have a table which has several field including:
contact_id
phone
phone_id
contact_id and phone are primary keys and phone_id is an auto increment field. I want to use it to recognize a certain entry. So I want to know that is it possible to duplicate that non primary field when I'm entering data.
Unless there is no constraint, some unique index, you can duplicate values in that column, because 1) you can turn identity_insert on, 2) you can reseed increments.
Here is a proof:
CREATE TABLE #test(id INT IDENTITY(1, 1))
INSERT INTO #test DEFAULT VALUES
INSERT INTO #test DEFAULT VALUES
INSERT INTO #test DEFAULT VALUES
SET IDENTITY_INSERT #test ON
INSERT INTO #test(id) VALUES(1)
SET IDENTITY_INSERT #test OFF
INSERT INTO #test DEFAULT VALUES
INSERT INTO #test DEFAULT VALUES
DBCC CHECKIDENT ('#test', RESEED, 1);
INSERT INTO #test DEFAULT VALUES
INSERT INTO #test DEFAULT VALUES
SELECT * FROM #test
DROP TABLE #test
Output:
id
1
2
3
1
4
5
2
3
The short answer is Yes, it's possible.
SQL Server does not force a unique constraint on identity columns, meaning that the can have duplicated values, however, Sql server will not generate duplicate values itself in an identity column.
Identity columns in sql server are populated by the sql server itself when you insert a row to the table.
However, you can specify a value to them by using SET IDENTITY_INSERT before the insert statement.
There are a couple of things that you should be aware of:
Setting identity_insert on is per table. you can only set it for one table at the time.
Until you set the identity_insert back off, any insert statement to that table will have to specify a value for the identity column.
you can't use set identity insert on for more then one table on a single session. therefor after you've done inserting records to the table you must set the identity_insert back off on that table.
I need to design a table in SQL Server having some columns, one of these columns (ID column and use sequential uniqueidentifier) should automatically populate its data when inserting other column data.
The values of the ID column should be generated automatically when insertion happens.
Please help me to do this, any help is appreciated.
NB: I am new to this step by step approach will be more helpful
Just create a table with a column ID of datatype uniqueidentifier and set it's default value to newsequentialid():
Then, when you go insert rows into that table, just omit the ID column from the list of columns you're inserted values into:
INSERT INTO dbo.YourTable(ColA, ColB, ....., ColX)
VALUES(.., .. ,. ...)
If you don't explicitly insert a value into ID, the default specification (newsequentialid()) will be used .
As per Marc_s's comment, you should use NEWSEQUENTIALID()
CREATE TABLE myTable (ColumnA uniqueidentifier DEFAULT NEWSEQUENTIALID());
See NEWSEQUENTIALID (Transact-SQL)
I have come across the following piece of T-SQL. Can somebody explain what it does.
INSERT #numbers default VALUES
The temporary table #numbers was created a few lines before with the following:
CREATE TABLE #numbers (num int identity primary key)
What does the "default values" bit do?
While I will never understand the need for the #numbers table, with just one column defined as identity, there is no other way to insert data into that table
INSERT #numbers default VALUES
will insert one row of data with the next IDENTITY value. The only alternate would be to use IDENTITY INSERT ON, which would be cumbersome in this case
The DEFAULT constraint is used to insert a default value into a column.
The default value will be added to all new records, if no other value is specified.
In your case, you just have an identity column which does not really correspond to a column with a specified default value.
How can I insert data into a column which has been defined as auto increment column using identity insert?please explain with an example.
If you have an "auto-increment" column - you really shouldn't be inserted specific values into that column yourself - after all, that's why it's an auto-increment column....
If you must do so after all - then you need to do:
SET IDENTITY_INSERT (your table name here) ON
INSERT INTO (your table name here) (IdentityCol, OtherCol1, .....)
VALUES( (new ID value), .......)
SET IDENTITY_INSERT (your table name here) OFF