The "Numbers" or "Tally" Table: What it is and how it replaces a loop.
- Luis Cazares - Thursday, March 7, 2019 6:32 PM
I have. No faster than a CTE tally in my experience.
"I cant stress enough the importance of switching from a sequential files mindset to set-based thinking. After you make the switch, you can spend your time tuning and optimizing your queries instead of maintaining lengthy, poor-performing code."-- Itzik Ben-Gan 2001
- Alan.B - Thursday, March 7, 2019 7:50 PM
Like I said, it's not by much but, as always, "It Depends".
--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.
"Change is inevitable... change for the better is not".
Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)
Intro to Tally Tables and Functions - Jeff Moden - Friday, March 8, 2019 9:33 AMAlan.B - Thursday, March 7, 2019 7:50 PM
Like I said, it's not by much but, as always, "It Depends".
I could be mistaken but I thought Luis was talking the performance of an in-memory tally table vs a traditional tally table.
I was looking for this yesterday and just found it: https://qa.sqlservercentral.com/Forums/1101315/Tally-OH-An-Improved-SQL-8K-CSV-Splitter-Function?PageIndex=36 It would appear that, in this case, the memory optimized table was faster but, for me, I have not had the same level of success. In my personal experience I have never seen a performance improvement switching from a CTE tally table to a memory optimized tally table.That said, I have never had a primary key on mine; here's the DDL for the one I use:
CREATE TABLE dbo.eTally
(
N INT NOT NULL,
UNIQUE NONCLUSTERED (N ASC)
)
WITH (MEMORY_OPTIMIZED = ON , DURABILITY = SCHEMA_ONLY);
The one Magoo used in his testing had a PK (nonclustered).On a separate note - here's a great example of "there being no spoon or default ORDER BY in SQL Server":
SELECT TOP (10) t.N
FROM dbo.eTally AS tReturns: 998753, 998754.....998762
"I cant stress enough the importance of switching from a sequential files mindset to set-based thinking. After you make the switch, you can spend your time tuning and optimizing your queries instead of maintaining lengthy, poor-performing code."-- Itzik Ben-Gan 2001
-
Ah... sorry, Alan. I flat out missed (even though bolded and underlined :blush:) that folks were talking about "memory optimized" tables. I can't speak to that because I don't use them... at least not yet. I can say that it's my understanding that "memory optimized" tables work the best for non-unique data and would speculate that there'd be little difference made by using them for a Tally Table. Again, I don't actually know because I've not tested it and probably won't in the near future.
--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.
"Change is inevitable... change for the better is not".
Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)
Intro to Tally Tables and Functions -
A minor point I came across today - your "favourite way" to produce the Tally table does not work in an Azure database:
SELECT TOP 11000 --equates to more than 30 years of dates
IDENTITY(INT,1,1) AS N
INTO dbo.Tally
FROM Master.dbo.SysColumns sc1,
Master.dbo.SysColumns sc2Access to Master.dbo.SysColumns not allowed.
You can change it to dbo.SysColumns - which seems to work fine.
-
Young man (or woman),
Implicit joins are evil. Always. Even in examples or practice exercises. Repent of your wicked ways.
- tom 69406 wrote:
A minor point I came across today - your "favourite way" to produce the Tally table does not work in an Azure database:
SELECT TOP 11000 --equates to more than 30 years of dates
IDENTITY(INT,1,1) AS N
INTO dbo.Tally
FROM Master.dbo.SysColumns sc1,
Master.dbo.SysColumns sc2Access to Master.dbo.SysColumns not allowed. You can change it to dbo.SysColumns - which seems to work fine.
Your point is well taken and it IS time to upgrade the article. I wrote this article about 12 years ago (2007) and (IIRC) I was still stuck in SQL Server 2000 where dbo.SysColumns hadn't been deprecated yet. I'm also one of those folks that won't publish code unless I've actually executed it and that's why I used deprecated but still working objects even though 2005 had been out for a couple of years.
That being said, here's what I normally use nowadays when I want a quick "row source" and don't happen to have my fnTally function available. Does it work in Azure?
SELECT TOP 11000
N = IDENTITY(INT,1,1)
INTO dbo.Tally
FROM sys.all_columns ac1
CROSS JOIN sys.all_columns ac2
;
ALTER TABLE dbo.Tally
ADD CONSTRAINT PK_Tally PRIMARY KEY CLUSTERED (N)
;--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.
"Change is inevitable... change for the better is not".
Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)
Intro to Tally Tables and Functions - david.holley wrote:
Young man (or woman), Implicit joins are evil. Always. Even in examples or practice exercises. Repent of your wicked ways.
BWAAA-HAAAA!!!!! Someone needs to tell MS that. Properly written correlated sub-queries require them.
--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.
"Change is inevitable... change for the better is not".
Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)
Intro to Tally Tables and Functions -
Don’t make me post some examples. The issue isn’t so much the implicit join but rather understanding the criteria in the WHERE statement when it contains the join information as well as any specific criteria. Especially when the {lengthy list of redacted adjectives} developers intermixed the two. Mix in an inline select on one side of the criteria and it goes South even faster.
- david.holley wrote:
Don’t make me post some examples. The issue isn’t so much the implicit join but rather understanding the criteria in the WHERE statement when it contains the join information as well as any specific criteria. Especially when the {lengthy list of redacted adjectives} developers intermixed the two. Mix in an inline select on one side of the criteria and it goes South even faster.
THAT's what I'm getting at. It's not the implicit joins that are the problem. They're merely a symptom of the rest that follows.
Still and like I said previously, correlated sub-queries work using implicit joins. In fact, the same equi-join manner using a WHERE clause that is so non--ANSI join.
--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.
"Change is inevitable... change for the better is not".
Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)
Intro to Tally Tables and Functions -
Are summary executions off the table?
-
Yes Jeff your new version works in Azure just fine
SELECT TOP 11000
N = IDENTITY(INT,1,1)
INTO dbo.Tally
FROM sys.all_columns ac1
CROSS JOIN sys.all_columns ac2
;I didn't realise sysColumns was deprecated - I've changed our version of the Tally table accordingly
Many Thanks
- Jeff Moden wrote:david.holley wrote:
Don’t make me post some examples. The issue isn’t so much the implicit join but rather understanding the criteria in the WHERE statement when it contains the join information as well as any specific criteria. Especially when the {lengthy list of redacted adjectives} developers intermixed the two. Mix in an inline select on one side of the criteria and it goes South even faster.
THAT's what I'm getting at. It's not the implicit joins that are the problem. They're merely a symptom of the rest that follows. Still and like I said previously, correlated sub-queries work using implicit joins. In fact, the same equi-join manner using a WHERE clause that is so non--ANSI join.
Are you saying that this:
SELECT
* -- I know, should be an actual column list
FROM
dbo.tableA as a, dbo.tebleB as b
WHERE
a.AJoinColumn = b.AJoinColumnis not ANSI Standard?
But it is, it is ANSI-89 Standard. With that, I personally never learned to use this style having started with the ANSI-92 style joins when I first started working with SQL Server 6.5 back in 1996.
-
I can’t speak as to the ANSI standards. I never knew that implicit joins existed until about 5 years ago despite being introduced to SQL 20 years ago. It was something about supporting a legacy app with code that makes a plate of spaghetti look lite a straight line.
- david.holley wrote:
I can’t speak as to the ANSI standards. I never knew that implicit joins existed until about 5 years ago despite being introduced to SQL 20 years ago. It was something about supporting a legacy app with code that makes a plate of spaghetti look lite a straight line.
Hey, I've seen that code before! It was a 1300-line trigger in Oracle that was used to balance out hours accounting records for a Baan ERP system where the ERP couldn't get it right. In inherited it from someone else, cleaned it up and organized it and got it to work, but it was still a mess. The original gave new meaning to spaghetti. I'm so thankful I don't live in that world any more.
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