I have created a table with employee id as identity column. Now, I want to remove identity and replace datatype as bigint. I am using Sql Compact edition. How to achieve this?
I don't believe you can, using TSQL, remove the IDENTITY property from a column.
Instead:
Add a new BIGINT column to the table
Copy the data from the current IDENTITY field into the new field
Drop the existing column
Rename the new column to the correct name
You can do it in SSMS in the Design view for the table. I believe behind the scenes it does something like above.
Update:
To confirm, in SSMS 2K8 when you try to remove the IDENTITY property from a column and then save it, it will actually recreate the table (you can see what it does exactly by monitoring in SQL Profiler). In order to do it in SSMS, you need to ensure you have the "Prevent saving changes that require table re-creation" option turned OFF in Tools-> Options -> Designers -> Table and Database Designers. I think it defaults to ON, which would result in an error message when you try to do it otherwise.
In "real" SQL Server, you'd have to do these steps - not sure if SQL Server CE allows the same, but give it a try! I'm assuming you probably have your PRIMARY KEY constraint on that column, too - right? If not, you don't need to do the first and last step. And I'm assuming you want to have the IDENTITY on the column again, right?
-- DROP the primary key constraint (if you have that on your column)
ALTER TABLE dbo.Employees
DROP CONSTRAINT PK__Employees__3214EC274222D4EF
-- ALTER the datatype into BIGINT
ALTER TABLE dbo.Employees
ALTER COLUMN Employee_ID BIGINT
-- set PK constraint again
ALTER TABLE dbo.Employees
ADD CONSTRAINT PK_Employees PRIMARY KEY(Employee_ID)
This should help - http://www.sqlmag.com/Files/23/22081/Listing_03.txt
Related
I have to change the auto increment on ID to explicitly define ID. For this I Go to
datatabse-> tables -> mytable -> design. There I set is dentity (under identity specification) to No. But when I click save it throws an error saying.
Saving changes is not permitted. The changes you have made require the following tables to
be droped and re created....
Is there any way to do it without dropping the table. I searched this error and got the solution to run a following query
SET IDENTITY_INSERT mytable ON GO
But when I try to insert from code, it throws error that
Cannot insert explicit value for identity column in table 'mytable' when IDENTITY_INSERT is set to OFF
Is there any way to get out of this problem
Once identity, always identity. You cannot change the identity property on a column. Technically, you could use IDENTITY_INSERT to get around it, but this requires setting the option on every single insert you do (this setting doesn't persist over sessions). This is probably not what you want.
Your only alternative, if recreating the table isn't an option, is to create a new column that isn't an identity column, then dropping the old one:
ALTER TABLE MyTable ADD NotAnID INT NULL;
GO
BEGIN TRANSACTION
UPDATE MyTable SET NotAnID = ID;
ALTER TABLE MyTable ALTER COLUMN NotAnID INT NOT NULL;
ALTER TABLE MyTable DROP COLUMN ID;
EXECUTE sp_rename 'MyTable.NotAnID', 'ID';
COMMIT;
This assumes your identity column is NOT NULL (as it usually is), that ID is not the primary key, that it isn't participating in foreign key constraints, and that you want the new column to take place of the old one.
If ID is the primary key, this exercise gets more involved because you need to drop the primary key constraint and recreate it -- which has its own challenges. Doubly so if it's also the clustered index. In this case, you are probably better off recreating the table anyway, because recreating the clustered index means the whole table is rewritten -- this will almost certainly interrupt production work, so you may as well let SSMS do the tough work for you. To allow that, go to Tools -> Options -> Designers and uncheck "Prevent saving changes that require table re-creation".
I have a column (which represents an e-mail) in a SQL Server database with varchar(50) as data type and I would like to make it unique (do not allow the same two e-mail addresses). I cannot find a way to make such column unique in SQL Server Management Studio.
How to do that?
In T-SQL it would be
ALTER TABLE MyTable WITH CHECK
ADD CONSTRAINT UQ_MyTable_Email UNIQUE (EmailAddress)
Or as an explicit index
CREATE UNIQUE INDEX IXU_Email ON MyTable (EmailAddress)
Edit: I can't see how to create a constraint in the SSMS GUI: other answers show how to manage indexes. I do only use SQL though, never the GUI for this kind of work
In the Object Explorer under the table right-click the Indexes folder and choose New Index....
In the window that appears enter Index name:, tick the Unique checkbox and add your email field from the Add... button then click OK.
Try this:
ALTER TABLE [dbo].[TableName] ADD CONSTRAINT UNQ__TableName__ColumnName UNIQUE ([ColumnName])
From this:
http://msdn.microsoft.com/en-us/library/ms191166.aspx
I am mass updating a SQL Server database. I am changing all our numeric(38,0) columns to int (yes, SQL Server scripts were created from Oracle scripts).
Using SMO and C# (I am a sw engineer), I managed to generate really nice scripts like SQL Server Management Studio would.
It all works very nicely except for one particular issue:
For a handful of tables, when I call
ALTER TABLE [myTable] ALTER COLUMN [columnA] INT
it decides to also change the column from NOT NULL to NULL. That, of course is a huge issue since I need to regenerate primary keys for most of those tables on those particular columns.
Obviously, I have plenty of options using SMO to find out which columns are primary keys and force them to be NOT NULL after or while I am updating the data type, but I am really curious as to what can be causing this.
Regards,
Eric.
Because in the absense of NOT NULL, the default is NULL.
ALTER TABLE [myTable]
ALTER COLUMN [columnA] INT NOT NULL
from ALTER TABLE (Transact-SQL)
When you create or alter a table with
the CREATE TABLE or ALTER TABLE
statements, the database and session
settings influence and possibly
override the nullability of the data
type that is used in a column
definition. We recommend that you
always explicitly define a column as
NULL or NOT NULL for noncomputed
columns.
In all my searching I see that you essentially have to copy the existing table to a new table to chance to identity column for pre-2008, does this apply to 2008 also?
thanks.
most concise solution I have found so far:
CREATE TABLE Test
(
id int identity(1,1),
somecolumn varchar(10)
);
INSERT INTO Test VALUES ('Hello');
INSERT INTO Test VALUES ('World');
-- copy the table. use same schema, but no identity
CREATE TABLE Test2
(
id int NOT NULL,
somecolumn varchar(10)
);
ALTER TABLE Test SWITCH TO Test2;
-- drop the original (now empty) table
DROP TABLE Test;
-- rename new table to old table's name
EXEC sp_rename 'Test2','Test';
-- see same records
SELECT * FROM Test;
we cannot add identity to an existing column using sql command but we can do it using GUI.
Right click on the table - design - select the column on which you want to add identity.
go to the properties available below. find the identity specification and set it to yes.
save the table.
if it is not saved the go to tools from the menu - options - table designer - uncheck the checkbox prevent saving changes. now you can save the table modifications.
now your existing table had identity.
In all of the new feature documents I read about 2008, adding identity to an existing column was not a feature I recall. The solution you've found is correct and I think the process of adding identity increment to a column automatically would be only rarely useful.
Well you can do something like this.
ALTER TABLE my_table ADD ID_COLUMN INT IDENTITY (1,1) NOT NULL
You can add the IDENTITY property to an existing column using the GUI of Enterprise Manager / Management Studio.
In SQL 2005 and earlier, you could not modify an existing column to become an identity column. I deem it very very unlikely that MS changed that in 2008.
In SQL Server (in my case, 2005) how can I add the identity property to an existing table column using T-SQL?
Something like:
alter table tblFoo
alter column bar identity(1,1)
I don't beleive you can do that. Your best bet is to create a new identity column and copy the data over using an identity insert command (if you indeed want to keep the old values).
Here is a decent article describing the process in detail:
http://www.mssqltips.com/tip.asp?tip=1397
The solution posted by Vikash doesn't work; it produces an "Incorrect syntax" error in SQL Management Studio (2005, as the OP specified). The fact that the "Compact Edition" of SQL Server supports this kind of operation is just a shortcut, because the real process is more like what Robert & JohnFX said--creating a duplicate table, populating the data, renaming the original & new tables appropriately.
If you want to keep the values that already exist in the field that needs to be an identity, you could do something like this:
CREATE TABLE tname2 (etc.)
INSERT INTO tname2 FROM tname1
DROP TABLE tname1
CREATE TABLE tname1 (with IDENTITY specified)
SET IDENTITY_INSERT tname1 ON
INSERT INTO tname1 FROM tname2
SET IDENTITY_INSERT tname1 OFF
DROP tname2
Of course, dropping and re-creating a table (tname1) that is used by live code is NOT recommended! :)
Is the table populated? If not drop and recreate the table.
If it is populated what values already exist in the column? If they are values you don't want to keep.
Create a new table as you desire it, load the records from your old table into your new talbe and let the database populate the identity column as normal. Rename your original table and rename the new one to the correct name :).
Finally if the column you wish to make identity currently contains primary key values and is being referenced already by other tables you will need to totally re think if you're sure this is what you want to do :)
There is no direct way of doing this except:
A) through SQL i.e.:
-- make sure you have the correct CREATE TABLE script ready with IDENTITY
SELECT * INTO abcTable_copy FROM abcTable
DROP TABLE abcTable
CREATE TABLE abcTable -- this time with the IDENTITY column
SET IDENTITY_INSERT abcTable ON
INSERT INTO abcTable (..specify all columns!) FROM (..specify all columns!) abcTable_copy
SET INDENTITY_INSERT abcTable OFF
DROP TABLE abcTable_copy
-- I would suggest to verify the contents of both tables
-- before dropping the copy table
B) Through MSSMS which will do exactly the same in the background but will less fat-fingering.
In the MSSMS Object Explorer right click the table you need to modify
Select "design" Select the column you'd like to add IDENTITY to
Change the identity setting from NO -> YES (possibly seed)
Ctr+S the table
This will drop and recreate the table with all original data in it.
If you get a warning:
Go to MSSMS Tools -> Options -> Designers -> Table and database Designers
and uncheck the option "Prevent saving changes that require table re-creation"
Things to be careful about:
your DB has enough disk space before you do this
the DB is not in use (especially the table you are changing)
make sure to backup your DB before doing it
if the table has a lot of data (over 1G) try it somewhere else first
before using in real DB
Create a New Table
SELECT * INTO Table_New FROM Table_Current WHERE 1 = 0;
Drop Column from New Table
Alter table Table_New drop column id;
Add column with identity
Alter table Table_New add id int primary key identity;
Get All Data in New Table
SET IDENTITY_INSERT Table_New ON;
INSERT INTO Table_New (id, Name,CreatedDate,Modified)
SELECT id, Name,CreatedDate,Modified FROM Table_Current;
SET IDENTITY_INSERT Table_New OFF;
Drop old Table
drop table Table_Current;
Rename New Table as old One
EXEC sp_rename 'Table_New', 'Table_Current';
alter table tablename
alter column columnname
add Identity(100,1)