How to make this the sample SQL Atomic? - sql-server

I have an store procedure,
ALTER PROCEDURE [dbo].[InsertDealGallery]
(
#ImageID INT,
#DealID INT
)
AS
DECLARE #MaxOrder INT;
SELECT #MaxOrder = MAX([Order]) + 1 FROM DealGallery WHERE DealID = #DealID
IF (#MaxOrder IS NULL)
BEGIN
SET #MaxOrder = 1;
END
INSERT INTO [DealGallery]
([ImageID]
,[DealID]
,[Order])
VALUES
(#ImageID
,#DealID
,#MaxOrder)
But I am fearing that this is not atomic because in the same time MaxOrder might remain same in concurrent thread. SO how to make this atomic?

Transactions is the feature to obtain atomic behavior. You know that a from ACID is for Atomic.
But you have choiced a very bad design, the aggegration function can lock all rows, performance becomes very poor.
Edited
You should move to identitat data type. Also another techniques exists, like counter table, but easy way is identity.
To enclose code into a transaction you should to include 'Begin transaction' and 'commit' sentences.
Edited 2
This approach, with a counter for each Deal, will avoid lock all DealGallery's rows, only lock DealGalleryCounter row.
CREATE TABLE DealGalleryCounter
(DealID INT not null primary key,
order int default 0
); -- Or add column to an existing deal table.
ALTER PROCEDURE [dbo].[InsertDealGallery]
(
#ImageID INT,
#DealID INT
)
AS BEGIN
DECLARE #order int
begin transaction
set transaction isolation level serializable
-- repeatable read is enough --
select #order = order + 1
from DealGalleryCounter
where #DealID = DealID
if #order is null
insert into DealGalleryCounter (DealID) values (#DealID)
INSERT INTO dbo.DealGallery (ImageID, DealID, [Order])
VALUES ( #ImageID, #DealID, #order );
update DealGallery
set DealGalleryCounter = #order
where #DealID = DealID;
commit; --or check for errors and rollback
END

Try this one -
ALTER PROCEDURE [dbo].[InsertDealGallery]
(
#ImageID INT,
#DealID INT
)
AS BEGIN
INSERT INTO dbo.DealGallery (ImageID, DealID, [Order])
SELECT
#ImageID
, #DealID
, ISNULL(MAX(d.[Order]) + 1, 1)
FROM (SELECT a = 1) t
LEFT JOIN dbo.DealGallery d ON d.DealID = #DealID
END
Or try this one -
INSERT INTO dbo.DealGallery (ImageID, DealID, [Order])
SELECT
#ImageID
, #DealID
, ISNULL(m, a)
FROM (SELECT a = 1) t
LEFT JOIN (
SELECT m = MAX(d.[Order]) + 1
FROM dbo.DealGallery d
WHERE d.DealID = #DealID
) t2 ON 1 = 1

This should work: insert max order increased by one when deal id is found in DealGallery table otherwise insert max order as 0
BEGIN TRAN
INSERT INTO [DealGallery]
([ImageID]
,[DealID]
,[Order])
SELECT #ImageID, #DealID, MAX([Order]) + 1
FROM DealGallery WHERE DealID = #DealID
UNION
SELECT #ImageID, #DeadID, 1
FROM (SELECT 1 AS C) AS T
WHERE NOT EXISTS (SELECT * FROM DealGallery WHERE DealID = #DealID)
COMMIT TRAN

Related

SQL Stored Procedure with Input parameters with While loop

I have a code below that should insert records into the table but unfortunately this code foes not work in case multiple records are inserted or updated or deleted. How should I rewrite the code for procedure to loop through all the inserted / deleted records? And I do need to use that stored procedure with Input parameters (not just simple insert into ... select ... from ...)
IF EXISTS (SELECT * FROM MyDB.sys.triggers WHERE object_id = OBJECT_ID(N'[dbo].[MyTable_DEL_UPD_INS]'))
DROP TRIGGER [dbo].[MyTable_DEL_UPD_INS]
GO
CREATE TRIGGER [dbo].[MyTable_DEL_UPD_INS]
ON [MyDB].[dbo].[MyTable]
AFTER DELETE, UPDATE, INSERT
NOT FOR REPLICATION
AS
BEGIN
DECLARE #PKId INT,
#Code VARCHAR(5),
#AuditType VARCHAR(10)
SET #Code = 'TEST'
IF EXISTS (SELECT * FROM deleted d)
AND NOT EXISTS (SELECT * FROM inserted i)
BEGIN
SELECT TOP 1
#PKId = d.[MyTable_PK],
#AuditType = 'DELETE'
FROM
deleted d WITH (NOLOCK)
IF #PKId IS NOT NULL
AND #Code IS NOT NULL
EXEC MyDB.[dbo].[SP_Audit] #PKId, #Code, #AuditType
END
IF EXISTS (SELECT * FROM deleted d)
AND EXISTS (SELECT * FROM inserted i)
BEGIN
SELECT TOP 1
#PKId = d.[MyTable_PK],
#AuditType = 'UPDATE'
FROM
deleted d WITH (NOLOCK)
IF #PKId IS NOT NULL
AND #Code IS NOT NULL
EXEC MyDB.[dbo].[SP_Audit] #PKId, #Code, #AuditType
END
IF NOT EXISTS (SELECT * FROM deleted d)
AND EXISTS (SELECT * FROM inserted i)
BEGIN
SELECT TOP 1
#PKId = d.[MyTable_PK],
#AuditType = 'INSERT'
FROM
deleted d WITH (NOLOCK)
IF #PKId IS NOT NULL
AND #Code IS NOT NULL
EXEC MyDB.[dbo].[SP_Audit] #PKId, #Code, #AuditType
END
END
GO
ALTER TABLE [MyDB].[dbo].[MyTable] ENABLE TRIGGER [MyTable_DEL_UPD_INS]
You should avoid using loops in triggers.
Triggers should be as quick to run as possible, since SQL Server will not return control to whatever statement that fired the trigger until the trigger is completed.
So instead of a loop, you should modify your SP_Audit procedure to work with multiple records instead of a single one.
usually, this is easily be done using a table valued parameter.
If you could post the SP_Audit as well, we could give you a complete solution.
Since you didn't post it, you can use these guidelines as a start:
First, you create a user defined table type:
CREATE TYPE dbo.Ids AS TABLE
(
Id int NOT NULL PRIMARY KEY
)
GO
Then, you create the procedure to use it:
CREATE PROCEDURE [dbo].[STP_Audit_MultipleRecords]
(
#IDs dbo.Ids readonly,
#Code CHAR(4),
#AuditType CHAR(6)
)
AS
-- Implementation here
GO
Last, your write your trigger like this:
CREATE TRIGGER [dbo].[MyTable_DEL_UPD_INS]
ON [MyDB].[dbo].[MyTable]
AFTER DELETE, UPDATE, INSERT
NOT FOR REPLICATION
AS
BEGIN
DECLARE #HasDeleted bit = 0,
#HasInserted bit = 0,
#AuditType CHAR(6),
#Code CHAR(4)
SET #Code = 'TEST'
DECLARE #IDs as dbo.Ids
IF EXISTS (SELECT * FROM deleted d)
SET #HasDeleted = 1
IF EXISTS (SELECT * FROM inserted i)
SET #HasInserted = 1
IF #HasDeleted = 1
BEGIN
IF #HasInserted = 1
BEGIN
SET #AuditType = 'UPDATE'
END
ELSE
BEGIN
SET #AuditType = 'DELETE'
END
END
ELSE
IF #HasInserted = 1
BEGIN
SET #AuditType = 'INSERT'
END
INSERT INTO #IDs (Id)
SELECT [MyTable_PK]
FROM inserted
UNION
SELECT [MyTable_PK]
FROM deleted
EXEC [dbo].[STP_Audit_MultipleRecords] #IDs, #Code, #AuditType
END
GO
Notes:
The #HasDeleted and #HasInserted variables are to allow you to only execute the EXISTS query once for every procedure.
Getting the primary key values from the deleted and inserted table is done using a single union query. Since union eliminates duplicate values, you can write this query just once. If you want to, you can write a different query for each audit type, but then you will have to repeat the same query 3 times (with different tables)
I've changed the data types of your #code and #AuditType variables to char, since they have a fixed length.

SQL Server : calling a stored procedure using table data

I may be wording this question very poorly but I am not 100% sure what I need to question.
I am trying to iterate over rows in a table and call a stored procedure using the data from the rows.
This is the code I already have, the problem with this is a timing issue (1000 rows takes around 1 minute);
--Set up a temp table with all non email alerts
SELECT TOP(1000)
RowNum = ROW_NUMBER() OVER(ORDER BY AlertID),
a.*, i.ImgData
INTO
#temp
FROM
dbo.ALERTS a
JOIN
dbo.IMAGES i ON i.VehicleID = a.VehicleID
WHERE
a.EmailImageSent = 0 OR a.EmailSent = 0
DECLARE #MaxRownum INT
SET #MaxRownum = (SELECT MAX(RowNum) FROM #temp)
DECLARE #Iter INT
SET #Iter = (SELECT MIN(RowNum) FROM #temp)
DECLARE #ImgData VARBINARY(MAX)
WHILE #Iter <= #MaxRownum
BEGIN
SELECT #VehicleID = VehicleID, #ImgData = ImgData
FROM #temp
WHERE RowNum = #Iter
IF #ImgData IS NOT NULL
BEGIN
EXEC dbo.someProcedure #VehicleID, #ImgData
--SELECT 'Image data found for', #VehicleID, #ImgData
END
SET #Iter = #Iter + 1
END
DROP TABLE #temp
Is there anyway I can run the stored procedure (dbo.someProcedure) while using a set based statement as the input?
Sorry if this has been asked before, I've had a look and couldn't find an answer or if this question isn't informative enough.
Thanks in advance
AFAIK sp_send_dbmail will need to be called once for each email, so either you have a loop here or you have a loop inside dbo.someProcedure.
Still I think that you could make some improvements. Use a FAST_FORWARD cursor rather than creating iteration variables and returning to the table each time to find the next row (thus creating 1000 table scans). Don't store redundant data in your #temp table, only what you need. This makes the table quicker to read.
Try this:
--Set up a temp table with all non email alerts
Create Table #temp (VehicleID int Primary Key Clustered, ImgData varbinary(max));
INSERT INTO #temp (VehicleID, ImgData)
SELECT TOP(1000)
a.VehicleID, i.ImgData
FROM
dbo.ALERTS a
JOIN
dbo.IMAGES i ON i.VehicleID = a.VehicleID
WHERE
a.EmailImageSent = 0 OR a.EmailSent = 0;
DECLARE #VehicleID int;
DECLARE #ImgData VARBINARY(MAX);
DECLARE Alert_Cursor Cursor Fast_Forward For (
Select VehicleID, ImgData From #temp);
OPEN Alert_Cursor;
FETCH NEXT FROM Alert_Cursor INTO #VehicleID, #ImgData;
WHILE ##FETCH_STATUS = 0
BEGIN
IF #ImgData IS NOT NULL
EXEC dbo.someProcedure #VehicleID, #ImgData;
FETCH NEXT FROM Alert_Cursor INTO #VehicleID, #ImgData;
END
CLOSE Alert_Cursor;
DEALLOCATE Alert_Cursor;
DROP TABLE #temp;

Count # of Rows in Stored Procedure Result, then Insert result into table

I have an SSIS package which will first run my sp_doSomething. This stored procedure will select data from several different tables and join them for possible storage into dbo.someTable. But I only want that IF the select is > 1 row of selected data.
I want to then have a precedence restraint that looks at the amount of rows my stored procedure returned.
If my row count > 1, then I want to take the results of the stored procedure and insert them into one of my tables.
Otherwise, I will record an error/send an email, or whatever.
I really don't want to run this stored procedure more then once, but that is the only way I could think to do it (Run it, count the rows. Then, run it again and insert the result).
I'm a complete TSQL/SSIS newb. So I'm sorry if this question is trivial.
I can't find a good answer anywhere.
Create a variable with Package Scope of type Int32 and name rowcount.
Data Flow
Control Flow
you can try this
declare #tableVar table(col1 varchar(100))
declare #Counter int
insert into #tableVar(col1) exec CompanyNames
set #Counter = (select count(*) from #tableVar)
insert into Anytable(col) Values (#counter)
Within the Stored Proc, write the results to a #Temp. Then Select Count(*) from the #Temp, into a variable.
Select #intRows = Count(*) from myTempResults
Then evaluate the value of #intRows.
If #intRows > 1 BEGIN
Insert Into dbo.SomeTable
Select * from #Temp
End
Will a #temp table work for you?
IF OBJECT_ID('tempdb..#Holder') IS NOT NULL
begin
drop table #Holder
end
CREATE TABLE #Holder
(ID INT )
declare #MyRowCount int
declare #MyTotalCount int = 0
/* simulate your insert, you would read from your real table(s) here */
INSERT INTO #HOLDER (ID)
select 1 union all select 2 union all select 3 union all select 4
Select #MyRowCount = ##ROWCOUNT, #MyTotalCount = #MyTotalCount + #MyRowCount
Select 'TheMagicValue1' = #MyRowCount, 'TheMagicTotal' = #MyTotalCount
INSERT INTO #HOLDER (ID)
select 5 union all select 6 union all select 7 union all select 8
/* you will note that I am NOT doing a count(*) here... which is another strain on the procedure */
Select #MyRowCount = ##ROWCOUNT, #MyTotalCount = #MyTotalCount + #MyRowCount
Select 'TheMagicValue1' = #MyRowCount, 'TheMagicTotal' = #MyTotalCount
/* Optional index if needed */
CREATE INDEX IDX_TempHolder_ID ON #Holder (ID)
/* CREATE CLUSTERED INDEX IDX_TempHolder_ID ON #Holder (ID) */
if #MyTotalCount > 0
BEGIN
Select 'Put your INSERT statement here'
END
/* this will return the data to the report */
Select ID from #HOLDER
IF OBJECT_ID('tempdb..#Holder') IS NOT NULL
begin
drop table #Holder
end

Batch updating using loop on large table

I have two tables with overlaping data. One table is about 90% duplicate of the other. I need to identify the 10% of unique records in a table and move it to it's parent table. Both of these tables are 400 million + rows with 300+ columns. The method I am attempting is adding a flag field to uniquely ID the records I need to transfer however I need to update the field and am struggling with the logic. Below is what I have put together so far and it causes a never ending loop. There are no null values in either table.
Declare #counter int
Declare #RowsEffected int
Declare #RowsCnt int
Declare #Err int
SELECT #COUNTER = 1
SELECT #RowsEffected = 0
while (#counter > 0)
begin
set Rowcount 10000000
update Table1
set Existsflg = 1
where exists (
Select Fields
from Table1
Except
Select Fields
from table2 )
Select #RowsCnt = ##ROWCOUNT , #Err = ##ERROR
If #Err <> 0
begin
Print 'Problem Updating the records'
end
IF #RowsCnt = 0
SELECT #COUNTER = 0
ELSE
SELECT #RowsEffected = #RowsEffected + #RowsCnt
PRINT 'The total number of rows effected :'+convert(varchar,#RowsEffected)
WAITFOR DELAY '00:00:10'
END
SET ROWCOUNT 0
Go
Thanks!
This is how I did it one time.
I didn't use RowCount, I used Select TOP (N) and "while exists"
My "source" dbo.Employee table was on another server.
GO
USE [$(DestinationDatabaseName)]
GO
/*
READ ME !!!
Replace
$(SourceServer).$(SourceDatabaseName)
With (the Server and DatabaseName of the SOURCE data)
(ex:) [OtherServer].[OtherDatabase]
*/
--SubFolder: SQLReplicateReplacer
print '[uspEmployeeReplicateReplacer]'
go
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[uspEmployeeReplicateReplacer]') AND type in (N'P', N'PC'))
DROP PROCEDURE [dbo].[uspEmployeeReplicateReplacer]
Go
/*
declare #numberRowsAffected int
declare #ErrorNumber int
exec [dbo].[uspEmployeeReplicateReplacer] #numberRowsAffected output , #ErrorNumber output
print #numberRowsAffected
print #ErrorNumber
print ''
*/
CREATE PROCEDURE [dbo].[uspEmployeeReplicateReplacer] (
#numberRowsAffected int output --return
,
#ErrorNumber int output
)
AS
SET NOCOUNT ON
select #ErrorNumber = 0
declare #ErrorTracker int
declare #insertRowCount int
declare #updateRowCount int
select #insertRowCount = 0
select #updateRowCount = 0
IF OBJECT_ID('tempdb..#Employeeupdate') IS NOT NULL
begin
drop table #Employeeupdate
end
CREATE TABLE #Employeeupdate (
EmployeeKeyID int IDENTITY (1,1),
EmployeeUUID uniqueidentifier,
EmployeeLabel varchar(64),
EmployeeDescription varchar(128)
)
declare #ManualReplicationRowCount int
/* I put this value in a stored procedure, so I could change it in one place */
/* EXEC dbo.uspInternalSettingGetManualReplicationRowCount #ManualReplicationRowCount output */
Select #ManualReplicationRowCount = 1000
declare #MaximumLoopCounter int
select #MaximumLoopCounter = 10000
while (#MaximumLoopCounter > 0) and exists
(
Select
TOP 1 null
from [$(SourceServer)].[$(SourceDatabaseName)].dbo.Employee vart with (nolock)
where not exists
(
select null from dbo.Employee with (nolock) -- destinationTable
Where
/*
destinationTable.SOMEUNIQUECOLUMN1 = sourceTable.SOMEUNIQUECOLUMN1
and
destinationTable.SOMEUNIQUECOLUMN2 = sourceTable.SOMEUNIQUECOLUMN2
*/
dbo.Employee.EmployeeUUID = vart.EmployeeUUID
)
)
BEGIN
select #MaximumLoopCounter = #MaximumLoopCounter - 1
DELETE FROM #Employeeupdate
Insert into #Employeeupdate
(
EmployeeUUID,
EmployeeLabel,
EmployeeDescription
)
Select
TOP (#ManualReplicationRowCount)
EmployeeUUID,
EmployeeLabel,
EmployeeDescription
from [$(SourceServer)].[$(SourceDatabaseName)].dbo.Employee vart with (nolock)
where not exists
(
select null from dbo.Employee with (nolock) -- destinationTable
Where
/*
destinationTable.SOMEUNIQUECOLUMN1 = sourceTable.SOMEUNIQUECOLUMN1
and
destinationTable.SOMEUNIQUECOLUMN2 = sourceTable.SOMEUNIQUECOLUMN2
*/
dbo.Employee.EmployeeUUID = vart.EmployeeUUID
)
SET NOCOUNT OFF
Insert into dbo.Employee
(
EmployeeUUID,
EmployeeLabel,
EmployeeDescription
)
Select
EmployeeUUID,
EmployeeLabel,
EmployeeDescription
from
#Employeeupdate
SELECT #insertRowCount = ##ROWCOUNT , #ErrorTracker = ##ERROR
if #ErrorTracker <> 0
BEGIN
select #ErrorNumber = #ErrorTracker
select #MaximumLoopCounter = 0 --Bail Out !!!
END
SET NOCOUNT ON
END --End While Loop
/*
SET NOCOUNT OFF
Update dbo.Employee
Set
--EmployeeUUID = vart.EmployeeUUID,
EmployeeLabel = vart.EmployeeLabel,
EmployeeDescription = vart.EmployeeDescription
From
dbo.Employee with (nolock) , [$(SourceServer)].[$(SourceDatabaseName)].dbo.Employee vart with (nolock)
Where
--Relationship
dbo.Employee.EmployeeUUID = vart.EmployeeUUID
SELECT #updateRowCount = ##ROWCOUNT
SET NOCOUNT ON
*/
SELECT #numberRowsAffected = #insertRowCount + #updateRowCount
print '/#Employeeupdate COUNT/'
print #numberRowsAffected
print '-------------------------'
IF OBJECT_ID('tempdb..#Employeeupdate') IS NOT NULL
begin
drop table #Employeeupdate
end
SET NOCOUNT OFF
GO
GRANT EXECUTE ON dbo.uspEmployeeReplicateReplacer TO $(DBUSERNAME)
GO
I’d suggest you do this in batches of 1M-5M at a time because you have a ton of data to update.
What I would do in this case is:
a) add new column named Processed (bit) that would be updated for all rows that are processed
b) select 1M rows into temp table (this may not be needed but it will make things a bit
cleaner)
c) insert all non-duplicate records into other table
d) update rows and mark them as processes

Is there a way to loop through a table variable in TSQL without using a cursor?

Let's say I have the following simple table variable:
declare #databases table
(
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
-- insert a bunch rows into #databases
Is declaring and using a cursor my only option if I wanted to iterate through the rows? Is there another way?
First of all you should be absolutely sure you need to iterate through each row — set based operations will perform faster in every case I can think of and will normally use simpler code.
Depending on your data it may be possible to loop using just SELECT statements as shown below:
Declare #Id int
While (Select Count(*) From ATable Where Processed = 0) > 0
Begin
Select Top 1 #Id = Id From ATable Where Processed = 0
--Do some processing here
Update ATable Set Processed = 1 Where Id = #Id
End
Another alternative is to use a temporary table:
Select *
Into #Temp
From ATable
Declare #Id int
While (Select Count(*) From #Temp) > 0
Begin
Select Top 1 #Id = Id From #Temp
--Do some processing here
Delete #Temp Where Id = #Id
End
The option you should choose really depends on the structure and volume of your data.
Note: If you are using SQL Server you would be better served using:
WHILE EXISTS(SELECT * FROM #Temp)
Using COUNT will have to touch every single row in the table, the EXISTS only needs to touch the first one (see Josef's answer below).
Just a quick note, if you are using SQL Server (2008 and above), the examples that have:
While (Select Count(*) From #Temp) > 0
Would be better served with
While EXISTS(SELECT * From #Temp)
The Count will have to touch every single row in the table, the EXISTS only needs to touch the first one.
This is how I do it:
declare #RowNum int, #CustId nchar(5), #Name1 nchar(25)
select #CustId=MAX(USERID) FROM UserIDs --start with the highest ID
Select #RowNum = Count(*) From UserIDs --get total number of records
WHILE #RowNum > 0 --loop until no more records
BEGIN
select #Name1 = username1 from UserIDs where USERID= #CustID --get other info from that row
print cast(#RowNum as char(12)) + ' ' + #CustId + ' ' + #Name1 --do whatever
select top 1 #CustId=USERID from UserIDs where USERID < #CustID order by USERID desc--get the next one
set #RowNum = #RowNum - 1 --decrease count
END
No Cursors, no temporary tables, no extra columns.
The USERID column must be a unique integer, as most Primary Keys are.
Define your temp table like this -
declare #databases table
(
RowID int not null identity(1,1) primary key,
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
-- insert a bunch rows into #databases
Then do this -
declare #i int
select #i = min(RowID) from #databases
declare #max int
select #max = max(RowID) from #databases
while #i <= #max begin
select DatabaseID, Name, Server from #database where RowID = #i --do some stuff
set #i = #i + 1
end
Here is how I would do it:
Select Identity(int, 1,1) AS PK, DatabaseID
Into #T
From #databases
Declare #maxPK int;Select #maxPK = MAX(PK) From #T
Declare #pk int;Set #pk = 1
While #pk <= #maxPK
Begin
-- Get one record
Select DatabaseID, Name, Server
From #databases
Where DatabaseID = (Select DatabaseID From #T Where PK = #pk)
--Do some processing here
--
Select #pk = #pk + 1
End
[Edit] Because I probably skipped the word "variable" when I first time read the question, here is an updated response...
declare #databases table
(
PK int IDENTITY(1,1),
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
-- insert a bunch rows into #databases
--/*
INSERT INTO #databases (DatabaseID, Name, Server) SELECT 1,'MainDB', 'MyServer'
INSERT INTO #databases (DatabaseID, Name, Server) SELECT 1,'MyDB', 'MyServer2'
--*/
Declare #maxPK int;Select #maxPK = MAX(PK) From #databases
Declare #pk int;Set #pk = 1
While #pk <= #maxPK
Begin
/* Get one record (you can read the values into some variables) */
Select DatabaseID, Name, Server
From #databases
Where PK = #pk
/* Do some processing here */
/* ... */
Select #pk = #pk + 1
End
If you have no choice than to go row by row creating a FAST_FORWARD cursor. It will be as fast as building up a while loop and much easier to maintain over the long haul.
FAST_FORWARD
Specifies a FORWARD_ONLY, READ_ONLY cursor with performance optimizations enabled. FAST_FORWARD cannot be specified if SCROLL or FOR_UPDATE is also specified.
This will work in SQL SERVER 2012 version.
declare #Rowcount int
select #Rowcount=count(*) from AddressTable;
while( #Rowcount>0)
begin
select #Rowcount=#Rowcount-1;
SELECT * FROM AddressTable order by AddressId desc OFFSET #Rowcount ROWS FETCH NEXT 1 ROWS ONLY;
end
Another approach without having to change your schema or using temp tables:
DECLARE #rowCount int = 0
,#currentRow int = 1
,#databaseID int
,#name varchar(15)
,#server varchar(15);
SELECT #rowCount = COUNT(*)
FROM #databases;
WHILE (#currentRow <= #rowCount)
BEGIN
SELECT TOP 1
#databaseID = rt.[DatabaseID]
,#name = rt.[Name]
,#server = rt.[Server]
FROM (
SELECT ROW_NUMBER() OVER (
ORDER BY t.[DatabaseID], t.[Name], t.[Server]
) AS [RowNumber]
,t.[DatabaseID]
,t.[Name]
,t.[Server]
FROM #databases t
) rt
WHERE rt.[RowNumber] = #currentRow;
EXEC [your_stored_procedure] #databaseID, #name, #server;
SET #currentRow = #currentRow + 1;
END
You can use a while loop:
While (Select Count(*) From #TempTable) > 0
Begin
Insert Into #Databases...
Delete From #TempTable Where x = x
End
Lightweight, without having to make extra tables, if you have an integer ID on the table
Declare #id int = 0, #anything nvarchar(max)
WHILE(1=1) BEGIN
Select Top 1 #anything=[Anything],#id=#id+1 FROM Table WHERE ID>#id
if(##ROWCOUNT=0) break;
--Process #anything
END
I really do not see the point why you would need to resort to using dreaded cursor.
But here is another option if you are using SQL Server version 2005/2008
Use Recursion
declare #databases table
(
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
--; Insert records into #databases...
--; Recurse through #databases
;with DBs as (
select * from #databases where DatabaseID = 1
union all
select A.* from #databases A
inner join DBs B on A.DatabaseID = B.DatabaseID + 1
)
select * from DBs
-- [PO_RollBackOnReject] 'FININV10532'
alter procedure PO_RollBackOnReject
#CaseID nvarchar(100)
AS
Begin
SELECT *
INTO #tmpTable
FROM PO_InvoiceItems where CaseID = #CaseID
Declare #Id int
Declare #PO_No int
Declare #Current_Balance Money
While (Select ROW_NUMBER() OVER(ORDER BY PO_LineNo DESC) From #tmpTable) > 0
Begin
Select Top 1 #Id = PO_LineNo, #Current_Balance = Current_Balance,
#PO_No = PO_No
From #Temp
update PO_Details
Set Current_Balance = Current_Balance + #Current_Balance,
Previous_App_Amount= Previous_App_Amount + #Current_Balance,
Is_Processed = 0
Where PO_LineNumber = #Id
AND PO_No = #PO_No
update PO_InvoiceItems
Set IsVisible = 0,
Is_Processed= 0
,Is_InProgress = 0 ,
Is_Active = 0
Where PO_LineNo = #Id
AND PO_No = #PO_No
End
End
It's possible to use a cursor to do this:
create function [dbo].f_teste_loop
returns #tabela table
(
cod int,
nome varchar(10)
)
as
begin
insert into #tabela values (1, 'verde');
insert into #tabela values (2, 'amarelo');
insert into #tabela values (3, 'azul');
insert into #tabela values (4, 'branco');
return;
end
create procedure [dbo].[sp_teste_loop]
as
begin
DECLARE #cod int, #nome varchar(10);
DECLARE curLoop CURSOR STATIC LOCAL
FOR
SELECT
cod
,nome
FROM
dbo.f_teste_loop();
OPEN curLoop;
FETCH NEXT FROM curLoop
INTO #cod, #nome;
WHILE (##FETCH_STATUS = 0)
BEGIN
PRINT #nome;
FETCH NEXT FROM curLoop
INTO #cod, #nome;
END
CLOSE curLoop;
DEALLOCATE curLoop;
end
I'm going to provide the set-based solution.
insert #databases (DatabaseID, Name, Server)
select DatabaseID, Name, Server
From ... (Use whatever query you would have used in the loop or cursor)
This is far faster than any looping techique and is easier to write and maintain.
I prefer using the Offset Fetch if you have a unique ID you can sort your table by:
DECLARE #TableVariable (ID int, Name varchar(50));
DECLARE #RecordCount int;
SELECT #RecordCount = COUNT(*) FROM #TableVariable;
WHILE #RecordCount > 0
BEGIN
SELECT ID, Name FROM #TableVariable ORDER BY ID OFFSET #RecordCount - 1 FETCH NEXT 1 ROW;
SET #RecordCount = #RecordCount - 1;
END
This way I don't need to add fields to the table or use a window function.
I agree with the previous post that set-based operations will typically perform better, but if you do need to iterate over the rows here's the approach I would take:
Add a new field to your table variable (Data Type Bit, default 0)
Insert your data
Select the Top 1 Row where fUsed = 0 (Note: fUsed is the name of the field in step 1)
Perform whatever processing you need to do
Update the record in your table variable by setting fUsed = 1 for the record
Select the next unused record from the table and repeat the process
DECLARE #databases TABLE
(
DatabaseID int,
Name varchar(15),
Server varchar(15),
fUsed BIT DEFAULT 0
)
-- insert a bunch rows into #databases
DECLARE #DBID INT
SELECT TOP 1 #DBID = DatabaseID from #databases where fUsed = 0
WHILE ##ROWCOUNT <> 0 and #DBID IS NOT NULL
BEGIN
-- Perform your processing here
--Update the record to "used"
UPDATE #databases SET fUsed = 1 WHERE DatabaseID = #DBID
--Get the next record
SELECT TOP 1 #DBID = DatabaseID from #databases where fUsed = 0
END
Step1: Below select statement creates a temp table with unique row number for each record.
select eno,ename,eaddress,mobno int,row_number() over(order by eno desc) as rno into #tmp_sri from emp
Step2:Declare required variables
DECLARE #ROWNUMBER INT
DECLARE #ename varchar(100)
Step3: Take total rows count from temp table
SELECT #ROWNUMBER = COUNT(*) FROM #tmp_sri
declare #rno int
Step4: Loop temp table based on unique row number create in temp
while #rownumber>0
begin
set #rno=#rownumber
select #ename=ename from #tmp_sri where rno=#rno **// You can take columns data from here as many as you want**
set #rownumber=#rownumber-1
print #ename **// instead of printing, you can write insert, update, delete statements**
end
This approach only requires one variable and does not delete any rows from #databases. I know there are a lot of answers here, but I don't see one that uses MIN to get your next ID like this.
DECLARE #databases TABLE
(
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
-- insert a bunch rows into #databases
DECLARE #CurrID INT
SELECT #CurrID = MIN(DatabaseID)
FROM #databases
WHILE #CurrID IS NOT NULL
BEGIN
-- Do stuff for #CurrID
SELECT #CurrID = MIN(DatabaseID)
FROM #databases
WHERE DatabaseID > #CurrID
END
Here's my solution, which makes use of an infinite loop, the BREAK statement, and the ##ROWCOUNT function. No cursors or temporary table are necessary, and I only need to write one query to get the next row in the #databases table:
declare #databases table
(
DatabaseID int,
[Name] varchar(15),
[Server] varchar(15)
);
-- Populate the [#databases] table with test data.
insert into #databases (DatabaseID, [Name], [Server])
select X.DatabaseID, X.[Name], X.[Server]
from (values
(1, 'Roger', 'ServerA'),
(5, 'Suzy', 'ServerB'),
(8675309, 'Jenny', 'TommyTutone')
) X (DatabaseID, [Name], [Server])
-- Create an infinite loop & ensure that a break condition is reached in the loop code.
declare #databaseId int;
while (1=1)
begin
-- Get the next database ID.
select top(1) #databaseId = DatabaseId
from #databases
where DatabaseId > isnull(#databaseId, 0);
-- If no rows were found by the preceding SQL query, you're done; exit the WHILE loop.
if (##ROWCOUNT = 0) break;
-- Otherwise, do whatever you need to do with the current [#databases] table row here.
print 'Processing #databaseId #' + cast(#databaseId as varchar(50));
end
This is the code that I am using 2008 R2. This code that I am using is to build indexes on key fields (SSNO & EMPR_NO) n all tales
if object_ID('tempdb..#a')is not NULL drop table #a
select 'IF EXISTS (SELECT name FROM sysindexes WHERE name ='+CHAR(39)+''+'IDX_'+COLUMN_NAME+'_'+SUBSTRING(table_name,5,len(table_name)-3)+char(39)+')'
+' begin DROP INDEX [IDX_'+COLUMN_NAME+'_'+SUBSTRING(table_name,5,len(table_name)-3)+'] ON '+table_schema+'.'+table_name+' END Create index IDX_'+COLUMN_NAME+'_'+SUBSTRING(table_name,5,len(table_name)-3)+ ' on '+ table_schema+'.'+table_name+' ('+COLUMN_NAME+') ' 'Field'
,ROW_NUMBER() over (order by table_NAMe) as 'ROWNMBR'
into #a
from INFORMATION_SCHEMA.COLUMNS
where (COLUMN_NAME like '%_SSNO_%' or COLUMN_NAME like'%_EMPR_NO_')
and TABLE_SCHEMA='dbo'
declare #loopcntr int
declare #ROW int
declare #String nvarchar(1000)
set #loopcntr=(select count(*) from #a)
set #ROW=1
while (#ROW <= #loopcntr)
begin
select top 1 #String=a.Field
from #A a
where a.ROWNMBR = #ROW
execute sp_executesql #String
set #ROW = #ROW + 1
end
SELECT #pk = #pk + 1
would be better:
SET #pk += #pk
Avoid using SELECT if you are not referencing tables are are just assigning values.

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