Can I reset cursor's position to the beginning?

问题

As in the topic. Can I simply reset cursor's position to the beginning in Transact-SQL, so it can run again over the table? I want to reset it in the following context:

DECLARE @userID INT
DECLARE user_cursor CURSOR FOR SELECT userID FROM users

WHILE /* some condition */
BEGIN
...

    FETCH NEXT FROM user_cursor INTO @userID

    IF @@FETCH_STATUS = 0
    BEGIN
        /*... here goes the reset of the cursor ...*/
    END

...
END

回答1:

you need to declare your cursor as scroll, like this

declare c scroll cursor for (select statement);

then at any time for locating to the first just use the following

fetch first from c;

回答2:

Another option that can be used that doesn't force you to change the type of cursor is simply to close the cursor and re-open it:

CLOSE user_cursor
OPEN user_cursor

But the scroll option will be cheaper in terms of resource usage, if that's a change you can accept.

回答3:

The data retrieved by the cursor will not change.

STATIC

Defines a cursor that makes a temporary copy of the data to be used by the cursor. All requests to the cursor are answered from this temporary table in tempdb; therefore, modifications made to base tables are not reflected in the data returned by fetches made to this cursor, and this cursor does not allow modifications.

回答4:

Use cursor loops and its taken care of for you...

cursor c_something IS
   select * from somewhere

BEGIN

    for some_row in c_something LOOP
        -- do stuff with some_row.COLUMN;
    END LOOP; -- this closes the cursor for you when it has gone all the way through

    -- do other stuff

    for some_row in c_something LOOP -- opens the cursor again from the top
        -- do stuff with some_row.COLUMN;
    END LOOP;

END;

来源：https://stackoverflow.com/questions/17317732/can-i-reset-cursors-position-to-the-beginning

标签

sql-server

tsql

database-cursor