wrong is_identity in sys.columns for inline functions

问题

I have a problem with sys.columns for inline functions.
Maybe an error of SQL Server or I'm missing something?

Let's start from beginning, I have a simple table and a simple function like these:

DROP TABLE [dbo].[SimpleTable]
GO

CREATE TABLE [dbo].[SimpleTable](
    [id] [int] IDENTITY(1,1) NOT NULL PRIMARY KEY CLUSTERED,
    [descr] [varchar](50) NULL
    )
GO

DROP VIEW SimpleView
GO

CREATE VIEW SimpleView
AS
SELECT * FROM SimpleTable
GO

DROP FUNCTION SimpleFunction
GO

CREATE FUNCTION SimpleFunction(
    @dummy INT = NULL
)
RETURNS TABLE
RETURN
SELECT * FROM SimpleTable
GO

I can insert a row into SimpleTable using both a direct "table insert" or indirect "function insert" like this:

INSERT INTO SimpleTable (descr) VALUES ('DIRECT TABLE INSERT');
INSERT INTO SimpleView (descr) VALUES ('VIEW INSERT');
INSERT INTO SimpleFunction(DEFAULT) (descr) VALUES ('INLINE FUNCTION INSERT');

SELECT * FROM SimpleTable;

yes, it works..

id  descr
1   DIRECT TABLE INSERT
2   VIEW INSERT
3   INLINE FUNCTION INSERT

When I try to insert rows with explicit NULLs or explicit values in column id both SimpleTable and SimpleFunction insert, behave the same way:

INSERT INTO SimpleTable (id, descr) VALUES (3, 'DIRECT TABLE INSERT')
INSERT INTO SimpleView (id, descr) VALUES (5, 'VIEW INSERT')
INSERT INTO SimpleFunction(DEFAULT) (id, descr) VALUES (4, 'INLINE FUNCTION INSERT')

Server: Msg 544, Level 16, State 1, Line 1
Cannot insert explicit value for identity column in table 'SimpleTable' when IDENTITY_INSERT is set to OFF.
Server: Msg 544, Level 16, State 1, Line 2
Cannot insert explicit value for identity column in table 'SimpleTable' when IDENTITY_INSERT is set to OFF.
Server: Msg 544, Level 16, State 1, Line 3
Cannot insert explicit value for identity column in table 'SimpleTable' when IDENTITY_INSERT is set to OFF.

and

INSERT INTO SimpleTable (id, descr) VALUES (null, 'DIRECT TABLE INSERT')
INSERT INTO SimpleView (id, descr) VALUES (NULL,'VIEW INSERT')
INSERT INTO SimpleFunction(DEFAULT) (id, descr) VALUES (null, 'INLINE FUNCTION INSERT')

Msg 339, Level 16, State 1, Line 1
DEFAULT or NULL are not allowed as explicit identity values.
Msg 339, Level 16, State 1, Line 2
DEFAULT or NULL are not allowed as explicit identity values.
Msg 339, Level 16, State 1, Line 3
DEFAULT or NULL are not allowed as explicit identity values.

So there is no difference and the column id is recognized and treated as identity in both ways.

But now, let's take a look into sys.columns:

SELECT o.name o_name, o.type, o.type_desc, c.name c_name, c.is_identity
FROM sys.objects o
JOIN sys.columns c on o.object_id = c.object_id
where o.name in ( 'SimpleTable', 'SimpleFunction')
and c.name = 'id' 

o_name          type    type_desc                           c_name  is_identity
SimpleTable     U       USER_TABLE                          id      1
SimpleView      V       VIEW                                id      1
SimpleFunction  IF      SQL_INLINE_TABLE_VALUED_FUNCTION    id      0

and also sys.dm_exec_describe_first_result_set (thanks to @Jeroen Mostert):

Type    name    source_table    source_column   is_identity_column  is_updateable   is_nullable is_part_of_unique_key
U       id      SimpleTable     id              1                   0               0           1
V       id      SimpleTable     id              1                   0               0           1
IF      id      SimpleTable     id              0                   1               0           1

As you can see, the identity column of SimpleTable is not marked as identity in function structure.

My question is WHY?

I'm using a DbCommandBuilder in .NET and it produces wrong queries because of that.

I have tried to manually change it but it is no more possible since SQL server 2008.

来源：https://stackoverflow.com/questions/40149576/wrong-is-identity-in-sys-columns-for-inline-functions

标签

.net

sql-server

sql-server-2012