问题
I have marked a column as Identity in my table
create table Identitytest(
number int identity(1,001) not null,
value varchar(500)
)
I need the identity column to be incremented as 001,002,003, etc.
The database shows that it is inserting as 1,2,3, etc.
How can this be done?
回答1:
If you want to display your number column with leading zeros, just pad it in your SELECT statement. It's a number, it will NOT store with leading zeros as an integer.
SELECT RIGHT('00000' + CAST([number] AS varchar(5)) , 3)
FROM IdentityTest
The 3 is the number of characters you want total in the output display.
回答2:
As the others have already rightfully pointed out - an INT never has leading zeroes - it just holds the value, that's all (and that's good that way).
If you need some additional formatting, you could always add a computed column to your table, something like:
ALTER TABLE dbo.Identitytest
ADD DisplayNumber AS RIGHT('000' + CAST(number AS VARCHAR(3)) , 3) PERSISTED
This way, your INT IDENTITY will be used as an INT and always contains the numerical value, while DisplayNumber contains 001, 002, ... 014, 015, ..... and so forth - automagically, always up to date.
Since it's a persisted field, it's now part of your table, and you can query on it, and even put an index on it to make queries faster:
SELECT value FROM dbo.IdentityTest WHERE DisplayNumber = '024'
And of course, you could use just about any formatting in the definition of your computed column, so you could also add a prefix or something:
ALTER TABLE dbo.Identitytest
ADD DisplayNumber
AS 'ABC-' + RIGHT('000' + CAST(number AS VARCHAR(3)) , 3) PERSISTED
So in this case, your DisplayNumber would be ABC-001, ABC-002, ... and so on.
You get the best of both worlds - you keep your INT IDENTITY which is numerical and automatically increased by SQL Server, and you can define a display format any way you like and have that available at any time.
回答3:
If you require both the auto-incrementing number (which can only be a number) and an alphabetic representation of the number, you might consider looking at computed columns.
Here's a few links to get you going:
- http://www.mssqltips.com/tip.asp?tip=1682
- http://msdn.microsoft.com/en-us/library/ms191250.aspx
- http://www.kodyaz.com/articles/sql-server-computed-column-calculated-column-sample.aspx
回答4:
Why do you need that? As an integer, 001 is the same as 1. If what you want is that for display or other purposes, create another column and do your work there (you may do it as part of a trigger on the table, on insert, that looks at the newly inserted row, and creates the entry in the column appropriately.
回答5:
i've got a table where i'm storing an integer, but the users want to see it a XXX, even if it has zeroes, so i wrote this code
declare @a int
set @a=1
select replicate('0',3-len(@a))+ cast(@a as varchar(4))
回答6:
Here is another method:
create table TEST_T (ui int NOT NULL identity, name varchar(10))
insert into TEST_T values ( 'FRED' )
select NAME, ui, RIGHT('0000' + LTRIM(STR(ui)), 4) as ui_T from TEST_T
go
/* NOTE: A view could be created with a calculated column instead of the identity column. */
create view TEST_V as select NAME, RIGHT('0000' + LTRIM(STR(ui)), 4) as ui_V from TEST_T go
go
select * from TEST_V
drop view TEST_V
drop table TEST_T
Not quite as much data duplication(?) as adding a column to the table and no need to specify the column in the select statement.
回答7:
I need the identity column to be incremented as 001,002,003, etc.
The database shows that it is inserting as 1,2,3, etc.
SQL databases store values, not the literals you used to write those values. 002 is 2. Just like 1 + 1 is 2. Would you expect SELECT 1 + 1 to display the string "1 + 1" instead of 2?
If you want the leading zeros to be stored in your column, you have to use a character type. But then you can't use AUTOINCREMENT/IDENTITY.
What you probably really want is something like printf("%03d", number) in program that reads from the database.
来源：https://stackoverflow.com/questions/3429284/sql-identity-with-leading-padded-zeros