Madhivanan

Populating sample data

Sometimes you may need some sample data for testing purpose

The following may help you in generating some sample data of different datatypes

select 
        abs(checksum(newid()))%10000 as intcol,
        abs(checksum(newid()))*rand()/100 as float_col,
        dateadd(day,0,abs(checksum(newid()))%100000) as date_col,
        substring(replace(cast(newid() as varchar(36)),'-',''),1,abs(checksum(newid()))%15) as varchar_col,
        abs(checksum(newid()))%2 as bit_col 
from 
        master..spt_values 
where 
        type='p' and 
        number between 1 and 200

Union Vs Union All

Well. Most of you know the diffrence between the two.

http://blog.sqlauthority.com/2007/03/10/sql-server-union-vs-union-all-which-is-better-for-performance/

http://www.codethinked.com/post/2007/11/UNION-versus-UNION-ALL2c-lessons-in-minutiae.aspx

Here is one of the differences that is not known by newbies

When you use UNION, you cant include any column of type TEXT and NTEXT. But it is possible if you use UNION ALL

Declare @test table(i int, text_col text)
insert into @test 

select 1,'some test string'union all
select 2,'some other test string'
 
--Error
select i,text_col from @test where i=1union 
select i,text_col from @test where i=1
--No Error
 select i,text_col from @test where i=1union all
select i,text_col from @test where i=1