I have a table which had an identity column.
for many reasons we had to remove the identity from that column.
I have a system that inserts a value to that table by the old way, passes null for the identity column.
is there a simple way to define identity column to receive a value in case it is passed to it, and if a value of null is passed, to make that table to set a unique value to that field that is not found in that table (act like identity).
What i mean is, if there is value, insert it.
And if the system tries to insert null act like an identity.
Thanks in advance.
A trigger seems like a good choice for this situation, but there are a lot of ways you can handle the situation.
The example below creates an INSTEAD OF insert trigger that gets the columns that were supposed to be inserted, and generates a new value via a function if the ID column is null.
CREATE TRIGGER myTrigger ON myTable
INSTEAD OF INSERT
AS
INSERT INTO myTable (myIDcolumn, anotherColumn)
SELECT COALESCE(myIDColumn, dbo.SomeMethodToCreateID), anotherColumn
FROM inserted
How that SomeTheodToCreateID function is to work is up to you. One thing you could do is change the SELECT to combine max plus row_number:
SELECT (COALESCE(myIDColumn,
(SELECT MAX(myIDColumn) FROM myTable) + ROW_NUMBER() OVER(ORDER BY anotherColumn)
)
...
Try This
DBCC CHECKIDENT ( '[dbo].[Customers]', RESEED, 1 )
Related
I need to update a SQL Server table periodically by inserting new records into it.
The table has an ID column in the form of Company0001 through Company0020 right now.
Let's say I added one record of a new company into the table. I want to fill the ID column with Company0021 for this new record. Can anyone suggest a way to do this?
Thank you so much!
I would strongly suggest to use an identity column. Identity is a mechanism designed and used for this actual purpose and therefore it would be much better in terms of performance.
Nevertheless, if you insist on IDs on the format 'CompanyXXX' I would suggest to use a varchar column. Then you would add a trigger on the insert and update operations. When the trigger runs, it would find out the last 'CompanyXXX' and form the new one. If you need help regarding triggers, you could check this tutorial.
Hope I helped!
My suggestion would be to have an autoincrement field, and then concatenate the company name with the ID.
If you don't want to do it with an ID field, do you want it to happen automatically, or are you going to manage it manually? If automatically, you'll need to write a trigger to intercept the INSERT and change the value there. Shouldn't be too hard to do.
I'd seriously recommend NOT doing this and going down the autoincrement field path. It's better.
Add another column to the table to hold an integer value (in this example SNo) and then write query as
declare #SNo int
select #SNo=max(SNo)+1 from Table_Name
insert into Table_Namevalues (#SNo,'company'+right('0000'+cast(#SNo as varchar(10)),4))
And then see the result
Hope this helps
In case a solution is required as, having only one column with values in desired format you can create a function as:
create table table1(id varchar(100));
Go
create function dbo.fn_GetCompanyIdentity ()
returns varchar(100)
as
begin
declare #CompanyIdentify varchar(100);
select #CompanyIdentify =
(select 'Company' +
right ('00000' + cast (
(
(
case when Not exists (select ROW_NUMBER() over( order by (select 1)) from Table1 ) then 1
else (select top 1 ROW_NUMBER() over( order by (select 1)) as currentRownumber from Table1 order by currentRownumber desc) + 1
end
)
)
as varchar(4))
,4));
return #CompanyIdentify;
end;
go
and then use the function in insert statement as :
insert into Table1 (id)
select dbo.fn_GetCompanyIdentity();
Go
Hope this helps!!
Why dont you just create an auto-increment column and then concatenate "Company" to this column in another column. And for presentation just select "Company+autoincrement" column.
I'm trying to get the last id inserted into a table.
I was using
SELECT IDENT_CURRENT('TABLE')
But the problem is that it doesn't return the last inserted id, it returns the max inserted id.
For example, if i do:
INSERT INTO 'TABLA' (ID) VALUES (100)
SELECT IDENT_CURRENT('TABLE') returns 100
but then if i do
INSERT INTO 'TABLA' (ID) VALUES (50)
SELECT IDENT_CURRENT('TABLE') returns 100
and I want to get 50
I need the ID of a specific table, and I generate the id dinamically, so it's not an identity
How can i do it?
From your code, it looks like ID is not an identity (auto-increment) column, so IDENT_CURRENT isn't going to do what you are expecting.
If you want to find the last row inserted, you will need a datetime column that represents the insert time, and then you can do something like:
SELECT TOP 1 [ID] FROM TABLEA ORDER BY [InsertedDate] DESC
Edited: a few additional notes:
Your InsertedDate column should have a default set to GetDate() unless your application, stored procs or whatever you use to perform inserts will be responsible for setting the value
The reason I said your ID is not an identity/auto-increment is because you are inserting a value into it. This is only possible if you turn identity insert off.
SQL Server does not keep track of the last value inserted into an IDENTITY column, particularly when you use SET IDENTITY_INSERT ON;. But if you are manually specifying the value you are inserting, you don't need SQL Server to tell you what it is. You already know what it is, because you just specified it explicitly in the INSERT statement.
If you can't get your code to keep track of the value it just inserted, and can't change the table to have a DateInserted column with a default of CURRENT_TIMESTAMP (which would allow you to see which row was inserted last), perhaps you could add a trigger to the table that logs all inserts.
SELECT SCOPE_IDENTITY()
will return the last value inserted in current session.
Edit
Then what you are doing is the best way to go just make sure that the ID Column is an IDENTITY Column, IDENT_CURRENT('Table_name'), ##IDENTITY and SCOPE_IDENTITY() returns last value generated by the Identity column.
If the ID column is not an Identity Column, all of these functions will return NULL.
How can I get the ##IDENTITY for a specific table?
I have been doing
select * from myTable
as I assume this sets the scope, from the same window SQL query window in SSMS I then run
select ##IDENTITY as identt
It returns identt as null which is not expected since myTable has many entrie in it already..
I expect it to return the next available ID integer.
myTable has a ID column set to Primary key and auto increment.
You can use IDENT_CURRENT
IDENT_CURRENT( 'table_name' )
Note that IDENT_CURRENT returns the last identity value for the table in any session and any scope. This means, that if another identity value was inserted after your identity value then you will not retrieve the identity value that you inserted.
You can only truly use SELECT ##IDENTITY after an insert - the last insert into a table that has an IDENTITY column is the value you'll get back.
You cannot "limit" it to a table - the value in ##IDENTITY - and by the way, I'd strongly recommend using SCOPE_IDENTITY() instead!! - is the last value on any IDENTITY column that was set.
The problem with ##IDENTITY is that it will report back the last IDENTITY value inserted into any table - if your INSERT into your data table will cause e.g. a trigger to write an entry into an Audit table and that Audit table has an IDENTITY field, you'll get back that IDENTITY value - not the one inserted into your table. SCOPE_IDENTITY() solves that.
IDENT_CURRENT does what you want. But don't.
This is in addition to marc_s' answer
I've never known ##IDENTITY to be used this way, i've only ever used it to access the ID of a newly inserted record.
That's correct. ##IDENTITY cannot be used the way you think it can be. It can only be used after an INSERT into a table. Let's consider this for a scenario:
You have two tables: Order (Primary Key: OrderID), OrderDetails (Foreign Key: OrderID)
You perform
INSERT INTO Order
VALUES('Pillows')
-- Note that OrderId is not mentioned in Values since it is auto number (primary key)
Now you want to perform insert into OrderDetail. But you don't always remember how many records there were in Order table prior to you having inserted the record for 'Pillows' and hence you don't remember what was the last PrimaryKey inserted into Order table. You could but even then you wouldn't want to specifically mention to insert (let's say OrderID of 1) when you insert into OrderDetail table.
Hence, your OderDetail insert would work kinda like so:
INSERT INTO OrderDetail
VALUES (##IDENTITY,'Soft Pillows')
Hope this explains the user of ##IDENTITY.
I have a table in a SQL Server database that has an auto-generated integer primary key. Without inserting a record into the table, I need to query the database and get what the next auto-generated ID number will be.
I think it's SQL Server version 2005, if that makes a difference.
Is there a way to do this?
Yes, but it's unreliable because another session might use the expected number.
If you still want to do this, use IDENT_CURRENT
Edit, as the comments have pointed out (improving my answer):
you need to add one IDENT_INCR('MyTable') to this to get the potential next number
another process may rollback and this number may not be the one used anyway
No, there is not. The ID will only ever be defined and handed out when the actual INSERT happens.
You can check the last given ID by using
DBCC CHECKIDENT('YourTableName')
but that's just the last one used - no guarantee that the next one is really going to be this value + 1 - it could be - but no guarantees
The only way to get a number that is guranteed not to be used by another process (i.e., a race condition) is to do the insert - is there any reason you can't do a NULL insert (i.e., just insert into the table with NULLs or default values for all other columns) and then subsequently UPDATE it?
i.e.,
CREATE TABLE bob (
seq INTEGER IDENTITY (1,1) NOT NULL,
col1 INTEGER NULL
)
GO
DECLARE #seqid INTEGER
INSERT INTO bob DEFAULT VALUES
SET #seqid = SCOPE_IDENTITY()
-- do stuff with #seqid
UPDATE bob SET col1 = 42 WHERE seq = #seqid
GO
You shouldn't use the technique in code, but if you need to do it for investigative purposes:
select ident_current(‘foo’) + ident_incr(‘foo’)
That gives you the last value generated + the incrementation for the identity, so should represent the next choice SQL would make without inserting a row to find out. This is a correct value even if a rollback has pushed the value forwards - but again, this is investigative SQL not stuff I would put in code.
The two values can also be found in the sys.identity_values DMV, the fields are increment_value and last_value.
Another way, depending on what your doing, is inserting whatever data goes into the table, and then using ##identity to retrieve the id of the record inserted.
example:
declare #table table (id int identity(1,1), name nvarchar(10))
insert into #table values ('a')
insert into #table values ('b')
insert into #table values ('c')
insert into #table values ('d')
select ##identity
insert into #table values ('e')
insert into #table values ('f')
select ##identity
This is pretty much a bad idea straight off the bat, but if you don't anticipate high volume and/or concurrency issues, you could just do something like this
select #nextnum = max(Id) + 1 from MyTable
I don't think thats possible out of the box in MS SQL (any version). You can do this with column type uniqueidentifier and using function NEWID().
For int column, you would have to implement your own sequential generator.
I have a temp table with the exact structure of a concrete table T. It was created like this:
select top 0 * into #tmp from T
After processing and filling in content into #tmp, I want to copy the content back to T like this:
insert into T select * from #tmp
This is okay as long as T doesn't have identity column, but in my case it does. Is there any way I can ignore the auto-increment identity column from #tmp when I copy to T? My motivation is to avoid having to spell out every column name in the Insert Into list.
EDIT: toggling identity_insert wouldn't work because the pkeys in #tmp may collide with those in T if rows were inserted into T outside of my script, that's if #tmp has auto-incremented the pkey to sync with T's in the first place.
SET IDENTITY_INSERT ON
INSERT command
SET IDENTITY_INSERT OFF
As identity will be generated during insert anyway, could you simply remove this column from #tmp before inserting the data back to T?
alter table #tmp drop column id
UPD: Here's an example I've tested in SQL Server 2008:
create table T(ID int identity(1,1) not null, Value nvarchar(50))
insert into T (Value) values (N'Hello T!')
select top 0 * into #tmp from T
alter table #tmp drop column ID
insert into #tmp (Value) values (N'Hello #tmp')
insert into T select * from #tmp
drop table #tmp
select * from T
drop table T
See answers here and here:
select * into without_id from with_id
union all
select * from with_id where 1 = 0
Reason:
When an existing identity column is selected into a new table, the new column inherits the IDENTITY property, unless one of the following conditions is true:
The SELECT statement contains a join, GROUP BY clause, or aggregate function.
Multiple SELECT statements are joined by using UNION.
The identity column is listed more than one time in the select list.
The identity column is part of an expression.
The identity column is from a remote data source.
If any one of these conditions is true, the column is created NOT NULL instead of inheriting the IDENTITY property. If an identity column is required in the new table but such a column is not available, or you want a seed or increment value that is different than the source identity column, define the column in the select list using the IDENTITY function. See "Creating an identity column using the IDENTITY function" in the Examples section below.
All credit goes to Eric Humphrey and bernd_k
Not with SELECT * - if you selected every column but the identity, it will be fine. The only way I can see is that you could do this by dynamically building the INSERT statement.
Just list the colums you want to re-insert, you should never use select * anyway. If you don't want to type them ,just drag them from the object browser (If you expand the table and drag the word, columns, you will get all of them, just delete the id column)
INSERT INTO #Table
SELECT MAX(Id) + ROW_NUMBER() OVER(ORDER BY Id)
set identity_insert on
Use this.
Might an "update where T.ID = #tmp.ID" work?
it gives me a chance to preview the data before I do the insert
I have joins between temp tables as part of my calculation; temp tables allows me to focus on the exact set data that I am working with. I think that was it. Any suggestions/comments?
For part 1, as mentioned by Kolten in one of the comments, encapsulating your statements in a transaction and adding a parameter to toggle between display and commit will meet your needs. For Part 2, I would needs to see what "calculations" you are attempting. Limiting your data to a temp table may be over complicating the situation.