Sql procedure loop while updating records using cursors

15-Jan-2020 13:13 by 10 Comments

Sql procedure loop while updating records using cursors

I am fairly new to sql and I've been doing my own projects so please bare with me.

If I read the question it talks about " have a few records that I wish to loop through and do something with each record".

So far in this series we've been concerned with simply reading data from tables using a cursor.

In this final part we'll look at how you can use a cursor to modify data as well.

Wherever possible, the declarative nature of the language should be exploited - expressing your code as a set-based query.

In my T-SQL code I always use set based operations.

I have been told these types of operations are what SQL Server is designed to process and it should be quicker than serial processing. I assume Microsoft created them for a reason so they must have a place where they can be used in an efficient manner.

I know cursors exist but I am not sure how to use them. In some circles cursors are never used, in others they are a last resort and in other groups they are used regularly.

In most cases you can easily write a single SQL query that will do what you need to get done in one action instead of looping through individual records.

DECLARE @My Cursor CURSOR; DECLARE @My Field Your Field Data Type; BEGIN SET @My Cursor = CURSOR FOR select top 1000 Your Field from dbo.table where Status ID = 7 OPEN @My Cursor FETCH NEXT FROM @My Cursor INTO @My Field WHILE @@FETCH_STATUS = 0 BEGIN /* YOUR ALGORITHM GOES HERE */ FETCH NEXT FROM @My Cursor INTO @My Field END; CLOSE @My Cursor ; DEALLOCATE @My Cursor; END; select top 1000 Table ID into #Control Table from dbo.table where Status ID = 7 declare @Table ID int while exists (select * from #Control Table) begin select top 1 @Table ID = Table ID from #Control Table order by Table ID asc -- Do something with your Table ID delete #Control Table where Table ID = @Table ID end drop table #Control Table select top 1000 Table ID into #Control Table from dbo.table where Status ID = 7 declare @Table ID int while exists (select * from #Control Table) begin select @Table ID = (select top 1 Table ID from #Control Table order by Table ID asc) -- Do something with your Table ID delete #Control Table where Table ID = @Table ID end drop table #Control Table CREATE TABLE #Temp Table ( ROWID int identity(1,1) primary key, HIERARCHY_ID_TO_UPDATE int, ) --create some testing data --INSERT INTO #Temp Table VALUES(1) --INSERT INTO #Temp Table VALUES(2) --INSERT INTO #Temp Table VALUES(4) --INSERT INTO #Temp Table VALUES(6) --INSERT INTO #Temp Table VALUES(8) DECLARE @MAXID INT, @Counter INT SET @COUNTER = 1 SELECT @MAXID = COUNT(*) FROM #Temp Table WHILE (@COUNTER The variable MAXID is used to LOOP through.

The first variable will hold the running total of Oscars while the second will be used to read each individual film's Oscars as the cursor moves through the record set.

Next, we'll declare our cursor, open it and move it to the first record.

The easiest way to declare a cursor that can be used to update records is to simply use the default cursor type: Using the code above will declare a cursor which can used to update records.

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