How to reuse a cursor in tsql from the begining - sql

Question

How to reuse a cursor in tsql from the beginning without changing its definition.
I saw this topic link but I dont know what to do after this
fetch first from c;
I used after this code :
WHILE ##FETCH_STATUS = 0
BEGIN
...
FETCH NEXT FROM c INTO #myVariable;
END;
CLOSE c;
DEALLOCATE c;
but it didnt work.

Answer 1

You can create a scroll cursor with read only and reset to the first record from the cursor when needed.
For example:
DECLARE #T TABLE (Id int, Num int);
insert into #T values (1,0),(2,0),(3,0);
DECLARE #ID INT;
DECLARE #Num INT;
DECLARE #Counter INT = 0;
DECLARE c SCROLL CURSOR FOR (SELECT Id, Num FROM #T) FOR READ ONLY;
OPEN c;
FETCH NEXT FROM c INTO #ID, #Num;
WHILE ##FETCH_STATUS = 0 AND #Counter <= 3
BEGIN
SET #Counter = #Counter + 1;
UPDATE #T SET num = #Counter WHERE Id = #ID;
IF #ID = 2
BEGIN FETCH FIRST FROM c INTO #ID, #Num; END;
ELSE
BEGIN FETCH NEXT FROM c INTO #ID, #Num; END;
END;
CLOSE c;
select * from #T;
Gets:
Id Num
1 3
2 4
3 0
Just be aware that the values you get from the cursor don't change.
Since there's only 1 open and close.

Answer 2

Try this:
IF OBJECT_ID('tempdb..#tmp') IS NOT NULL
BEGIN
DROP TABLE #tmp;
END;
CREATE TABLE #tmp (num INT IDENTITY(10,10))
-- **** execute separately ****
INSERT INTO #tmp DEFAULT VALUES
GO 10
-- ****************************
DECLARE c scroll cursor for select num FROM #tmp;
OPEN c;
DECLARE #i int = 1,
#cursor_value INT;
WHILE #i < 10
BEGIN
IF ##FETCH_STATUS = 0 AND #i = 5
BEGIN
FETCH FIRST FROM c INTO #cursor_value;
END
ELSE
FETCH NEXT FROM c INTO #cursor_value
SELECT #i AS cntr, #cursor_value AS crsr
SET #i +=1
END
close c
DEALLOCATE c