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Auto Increment Alphabet


Auto Increment Alphabet

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Jeff Moden
Jeff Moden
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Alright... here you go. First, we'll demo a way to accomplish the task and then I'll show in the post following this one why this type of numbering should NEVER be done.

The way the following code works is that it actually uses an IDENTITY column to provide a true auto-incrementing capability instead of having to do any manual sequencing. That's important because instead of using a bunch of self joins to an "external number generator" or sequencer of any kind, we can use a Computed Column, instead.

I still think this type of "numbering" is a huge mistake (see the next post down for why).

--===== Create a table with a real auto-incrementing column and
-- a persisted formula to convert it to Base 26 automatically.
-- The auto-incrementing column is "Zero Based" to keep things simple.
-- Max value = 26^7-1 = 8,031,810,175 > Largest INT
CREATE TABLE #MyHead
(
MyHeadID INT IDENTITY(0,1) NOT NULL,
Base26ID AS CHAR(MyHeadID/308915776%26+65) --26^6
+ CHAR(MyHeadID/11881376%26+65) --26^5
+ CHAR(MyHeadID/456976%26+65) --26^4
+ CHAR(MyHeadID/17576%26+65) --26^3
+ CHAR(MyHeadID/676%26+65) --26^2
+ CHAR(MyHeadID/26%26+65) --26^1
+ CHAR(MyHeadID%26+65) --26^0
PERSISTED NOT NULL,
SomeString VARCHAR(36) NOT NULL
)

--===== Add a million+1 rows of "something" to the table
-- just to prove it works.
INSERT INTO #MyHead
(SomeString)
SELECT TOP 1000001
NEWID() AS SomeString
FROM Master.sys.All_Columns ac1
CROSS JOIN Master.sys.All_Columns ac2

--===== Show what's in the table
SELECT *
FROM #MyHead




--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

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Jeff Moden
Jeff Moden
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@Ankit (or anyone else who thinks this type of "numbering" is a good idea),

Let me tell you why BASE 26 "numbering" like this is SO bad that it'll likely get your company sued... try the following code with your choice of classic "3 and 4 letter" swear words and see what you get...


SELECT * FROM #MyHead WHERE Base26ID LIKE '%CRAP%'



Every soccer mom and little old lady in the world will be out to get you and your company if these numbers ever are exposed publicly.;-)

--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

Helpful Links:
How to post code problems
How to post performance problems
Forum FAQs
Jeff Moden
Jeff Moden
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Even though I still don't like this kind of "numbering", let's try things in a slightly different manner. If we remove all the vowels from the alphabet, it's a wee bit more difficult to spell swear words.

First, build the following scalar function. It's got to be scalar because we're still going to use it in a computed column. It can't be persisted, either, because it ends up being non-deterministic in this case and I haven't tried to figure out how to make it so because it actually runs faster than the previous example...

 CREATE FUNCTION dbo.Base21
--===== This function accepts an integer and returns mostly harmless
-- "numbering" using letters with all vowels removed.
-- Jeff Moden
(@Integer INT)
RETURNS VARCHAR(8) AS
BEGIN
DECLARE @Return VARCHAR(8)
;

WITH
cteAllowed AS
(
SELECT 'BCDFGHJKLMNPQRSTVWXYZ' AS Letters
)
SELECT @Return =
SUBSTRING(Letters, @Integer/1801088541%21+1, 1) --21^7
+ SUBSTRING(Letters, @Integer/85766121%21+1, 1) --21^6
+ SUBSTRING(Letters, @Integer/4084101%21+1, 1) --21^5
+ SUBSTRING(Letters, @Integer/194481%21+1, 1) --21^4
+ SUBSTRING(Letters, @Integer/9261%21+1, 1) --21^3
+ SUBSTRING(Letters, @Integer/441%21+1, 1) --21^2
+ SUBSTRING(Letters, @Integer/21%21+1, 1) --21^1
+ SUBSTRING(Letters, @Integer%21+1, 1) --21^0
FROM cteAllowed
;
RETURN @Return
END
GO



Now we can do this without all the swear words...


--===== Create a table with a real auto-incrementing column and
-- a persisted formula to convert it to Base 21 (no vowels) automatically.
-- The auto-incrementing column is "Zero Based" to keep things simple.
CREATE TABLE #MyHead
(
MyHeadID INT IDENTITY(0,1) NOT NULL,
Base21ID AS dbo.Base21(MyHeadID)
,
SomeString VARCHAR(36) NOT NULL
)

--===== Add a million+1 rows of "something" to the table
-- just to prove it works.
INSERT INTO #MyHead
(SomeString)
SELECT TOP 1000000
NEWID() AS SomeString
FROM Master.sys.All_Columns ac1
CROSS JOIN Master.sys.All_Columns ac2

--===== Show what's in the table
SELECT *
FROM #MyHead




--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

Helpful Links:
How to post code problems
How to post performance problems
Forum FAQs
Jeff Moden
Jeff Moden
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Group: General Forum Members
Points: 216076 Visits: 41986
The lack of feedback on this post has me worried that the OP is actually using the alphabetic increment in the unfiltered mode. Please save your company a lawsuit and don't do it.

--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

Helpful Links:
How to post code problems
How to post performance problems
Forum FAQs
ColdCoffee
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Goodness me, i lost track of this thread and now i saw that this alpha-numbering is a huge swear-word dump-yard.. hmmm,as u said Jeff, it will invite lawsuits.. lets wait for the OP to post back his thoughts...
Ankit Mathur-481681
Ankit Mathur-481681
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Hi Guys,

I'm so sorry I couldn't pitch in before.


Wayne - Well, you did say you only needed it to get to AAAA. ZZZZ is much higher! ;-)


@Wayne: Desires are insatiable :-P


Jeff - The lack of feedback on this post has me worried that the OP is actually using the alphabetic increment in the unfiltered mode. Please save your company a lawsuit and don't do it.


@Jeff: Yep .. you are right Jeff. Frankly, I didn't thought all that far. Your posts are enlightening.

As for lack on feedback on your attempts. I hope it doesn't put you both off but pardon my knowledge of Base 26 numbers. Its a new concept for me as I haven't used or, seen it being used anywhere so far & all this while I was & am actually trying to gain knowledge of Base 26 numbering system so that I can actually understand & implement your code.

Ankit
Jeff Moden
Jeff Moden
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Thanks for the feedback, Ankit...

There's a fair bit of complexity to using a base 26 "numbering" system like this even if you don't take into account all the swear words that can be realized. I still recommend avoiding it if you can.

--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

Helpful Links:
How to post code problems
How to post performance problems
Forum FAQs
rajesh_somvanshi
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Very Nice...thank you so much.
webridges
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I needed something to increment alphabetically for labeling revisions and stumbled across this thread. I tried several of the "mathematical" ways at attempting BASE26, but I could never get it to work since I needed A to be 1 and a leading blank/null to be 0 so that Z would roll to AA, etc. So I just went at it from another angle of simply dealing with the characters themselves.

In case anyone else has the need, this is what I ended up with: (Could be cleaned up, but this leaves it somewhat readable.)

DECLARE @Revision VARCHAR(20) = 'Z'; -- String to increment
DECLARE @Characters VARCHAR(50) = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'; -- Characters to use

DECLARE @CarryOver INT = 0;
DECLARE @Interation INT = 0;
DECLARE @CharIndex INT;
WHILE @CarryOver > 0
OR @Interation = 0
BEGIN
IF @Interation >= LEN(@Revision)
BEGIN
SET @Revision = SUBSTRING(@Characters, @CarryOver, 1) + @Revision;
SET @CarryOver = @CarryOver / LEN(@Characters);
END;
ELSE
BEGIN
SET @CharIndex = CHARINDEX(SUBSTRING(REVERSE(@Revision), @Interation + 1, 1), @Characters) + 1;
SET @Revision = STUFF(@Revision, LEN(@Revision) - @Interation, 1, SUBSTRING(@Characters, @CharIndex % LEN(@Characters), 1));
SET @CarryOver = @CharIndex / LEN(@Characters);
END;
SET @Interation = @Interation + 1;
END;
SELECT @Revision;


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