Monday, May 30, 2011

UNIQUEIDENTIFIER with ROWGUIDCOL

Example 1 :

CREATE TABLE MyTable (ID UNIQUEIDENTIFIER PRIMARY KEY DEFAULT NEWID(), nam varchar(max))


insert into MyTable (nam) values ('mohamed')
insert into MyTable (nam) values ('tareq')
insert into MyTable (nam) values ('emad')
insert into MyTable (nam) values ('ahmed')
select * from MyTable

Example 2 :

CREATE TABLE MyTable2 (ID UNIQUEIDENTIFIER ROWGUIDCOL PRIMARY KEY DEFAULT NEWSEQUENTIALID() , nam varchar(max))


insert into MyTable2 (nam) values ('mohamed')
insert into MyTable2 (nam) values ('tareq')
insert into MyTable2 (nam) values ('emad')
insert into MyTable2 (nam) values ('ahmed')
select * from MyTable2
select ROWGUIDCOL from MyTable2
select OBJECTPROPERTY (object_id('table1'),'TableHasRowGuidCol')

--Notes


--1) The UNIQUEIDENTIFIER along with ROWGUIDCOL NEWSEQUENTIALID() is far more efficient than normal UNIQUEIDENTIFIER along with NEWID().

--2) The Unique Ids generated with the second approach are sequential in nature, similar to IDENTITY values.

--3) There can be max of one ROWGUIDCOL for a table.

--4) You can query the table for ROWGUIDCOL. Example: SELECT ROWGUIDCOL FROM MyTable

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