An interesting thing happened to me yesterday. A coworker came up to me and asked, “Did you write this SQL statement?” After looking at it I realized it was a statement I had written about a year ago. In this statement, I had come up with a clever way of creating what is essentially a SQL identity column. The first thought that came to my mind was “What an idiot! I could have just added an identity column to the table!” But what my coworker noticed, that I did not, is that this statement has powerful implications.
alter table temp_your_table add Reference_Number int declare @intCounter int set @intCounter = 1000 update temp_your_table SET @intCounter = Reference_Number = @intCounter + 1
The neat thing about this statement is that it can be used, instead of a loop, to mathematically manipulate a column. For example you could add a column of Fibonacci numbers! I’m not sure why a person would need a column of Fibonacci numbers, but it’s empowering to know that you could. 😉 There are probably several other neat applications that could be done with this approach.
Truth be told, things like this happen when a college grad with limited SQL knowledge, but an abundance of C++ education, begins learning SQL.
** UPDATE **
** 5/16/2006 **
Well I found a great use for the SQL statement above. For a recent project I needed to create a region specific drop down list of languages. If a user is visiting our Spanish site their drop down list needs to include the Spanish spellings of our language options in alphabetical order, BUT with EspaÃ±ol on top of the list. Likewise, if the user is visiting our Portuguese site they need to see the list of languages with the Portuguese spelling, but with Portuguese on top.
To do this I sorted my list of languages in alphabetical order into a temp table with an “OrderNumber” column. Then I updated the “OrderNumber” column with an incrementing integer starting with 1. Next I updated my temp table, setting the “OrderNumber” of the default language to 0. Finally, I return the temp table ordered on my “OrderNumber” column. The whole procedure looks like the following. (I highlighted the “Haunted SQL Statement” from above in red.):
CREATE procedure GetLocalLanguageNameList @LanguageCode varchar(8) as
set nocount on
-- Find the ID of the Language the Page is Requesting
declare @LocalLanguageId as int
set @LocalLanguageId = (select LanguageId from Language where LanguageCode = @LanguageCode)
-- Get a list of alternative languages in the native tongue of the user
-- Add OrderNumber so we can use it to put the original Page Language ontop
-- Sore the alternative languages in alphabetical order
select l.LanguageCode, lln.LanguageName, 0 as OrderNumber
from dbo.LocalLanguageName lln
join dbo.Language l on lln.LanguageId = l.LanguageId
where lln.LocalLanguageId = @LocalLanguageId
order by lln.LanguageName
-- Number our languages in alphabetical order
declare @intCounter int
set @intCounter = 1
SET @intCounter = OrderNumber = @intCounter + 1
-- Update the placement of the current pages language to the front of our list
set OrderNumber = 0
where LanguageCode = @LanguageCode
-- Display the list in our final order
select LanguageCode, LanguageName
order by OrderNumber