SQL Term 'Cursor'

[Skittle]

I would like to clarify in my own mind what a 'cursor' is within SQL.

Whenever I hear the phrase I associate it with a row by row scripted loop through a table to do some fancy
row by row work. It's effectively a DO WHILE loop to read all rows one at a time and do something to it within the loop. I have an old example I made a note of years ago below.

However I often see the phrase ‘cursor’ used in more conceptual descriptions that do not relate to a hard coded loop.

For example:-
In a book description covering CROSS APPLY, I have the text ‘You don’t want to use a cursor to iterate through the suppliers table one at a time and invoke a separate query for each’.

Question
Am I correct that in the context of the above text a ‘cursor’ be considered any statement that reads through all rows in a select statement?


Context

--
--We Declare The Cursor To Equal A SQL Statement
DECLARE MyCursor CURSOR 
		     SCROLL 		
     DYNAMIC
FOR
		SELECT OHORDN, OHSALA, OHCUST, OHCOMP FROM FGBOIH
		WHERE OHSALA = ‘A1’



--
--Next We Declare The Local Variables To Hold The ‘Record Format’
DECLARE @Order Char(6),
        @SalesArea Char(2),
        @Customer Char(6),
        @Company Char(2)

--
--We Now Open The Cursor ( Lock of selection begins )
OPEN MyCursor


	Read Ahead ( no and type of vars must match SELECT )
	FETCH NEXT FROM MyCursor INTO @Order, 
					 	@SalesArea,
						@Customer,
						@Company

	
--
	--Loop Through Cursor Until Fetch Status Indicates Failure
	WHILE @@FETCH_STATUS = 0 BEGIN

			--Read Next
			FETCH NEXT FROM MyCursor INTO @Order, 
					 	@SalesArea,
						@Customer,
						@Company
	END	



--
--We Close The Cursor ( Locks of selection end )
CLOSE MyCursor

Dazed and confused.

Remember.. 'Depression is just anger without enthusiasum'.

 

[Olaf Doschke]

I don't know how you think this is not referring to the exact meaning of a cursor. Yes, this is talking about cursors.
You won't want a per row of a cursor parameterized query but a join instead, as the means one (hopefully/normally well optimizable) query instead of N (also normally optimizable but less good optimizable) queries.

Bye, Olaf.

 

[johnherman]

CURSOR is an acronym for CURrent Set Of Rows. It's the set of data returned by a SQL query. That said, the word cursor is usually applied to a set of data returned by a query that is accessed by the application one row at a time (FETCH records). Each database has extensions to the ANSI-SQL language to handle cursors. Oracle=PL/SQL, Sybase and Microsoft = Transact-SQL, etc.

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