pseudo column is a act as an database table column,but its not a actual column in a table,we can fetch value from a pseudo column. ex. user,usid,rownum,rowid,level,nextval,curval,sysdate

It is the column, which is not available in the Database table physically. ex. select user

A pseudocolumn behaves like a table column, but is not actually stored in the table. You can select from pseudocolumns, but you cannot insert, update, or delete their values.

A pseudocolumnis a one who behave likes a column of a table but that table doesn't exists physically. In SQL server Inserted table and Deleted table can be refers to as pseudocolumn.

Try this: CREATE TABLE t(x INT IDENTITY, y UNIQUEIDENTIFIER ROWGUIDCOL) SELECT $IDENTITY, $ROWGUID FROM t

I'm not aware of any other pseudocolumn, except $IDENTITY and $ROWGUID. $PARTITION looks more like a special keyword needed for a function call.

Razvan

Pseudocolumns are indirect references to specific columns in a table. For example, the pseudocolumn $IDENTITY will return the value of the identity field within a given table. For example:

CREATE TABLE #test (i1 int IDENTITY(1,1), d1 varchar(10))
INSERT INTO #test (d1) VALUES ('Row 1')
SELECT $identity FROM #test AS t

The select statement returns a recordset showing column i1 by name, and all of its values.

When selecting against a table that does not have the specified pseudocolumn, the query returns the following error (for $rowguid):

SELECT $rowguid FROM #test AS t
---------
Msg 207, Level 16, State 1, Line 1
Invalid column name '$rowguid'.

Simply adding a uniqueidentifier to the table will not remove this error. Instead, you need to add a column with the ROWGUIDCOL property:

ALTER TABLE #test ADD guidcol uniqueidentifier CONSTRAINT Guid_Default DEFAULT NEWID() ROWGUIDCOL

Selecting $ROWGUID at this point will return the values in the guidcol column.

As far as I know, $IDENTITY and $ROWGUID are the only defined pseudocolumns in SQL Server. The $PARTITION value may or may not also be considered a pseudocolumn, but it works on table partitions instead. Since partitions are not columns, I do not consider it to be a pseudocolumn.