How to check if a cursor exists (open status)

sql

cursor-status

error-handling

best-practices

byAlex Kataev·Oct 21, 2024

Rapidly assess the condition of your SQL cursor via the CURSOR_STATUS function. Seek a positive number if the cursor has been fetched and is open, -1 for an open but unfetched cursor, and 0 or -2 if the cursor is closed or nonexistent.

DECLARE @status INT;
SET @status = CURSOR_STATUS('global', 'YourCursorName');

IF @status > 0
    PRINT 'Cursor Open & Fetched.';
ELSE IF @status = -1
    PRINT 'Cursor Open & Unfetched.';
ELSE 
    PRINT 'Cursor Closed or Nonexistent.';

Just exchange 'YourCursorName' for your unique cursor moniker. This block of code provides immediate results regarding the cursor status.

Ensure your cursor lifecycle is a "live long and prosper" one

Ensure cursor existence and appropriate state by invoking CURSOR_STATUS before fetching, closing, or deallocating. Here's how:

Track cursor usage: Since complex scripts can easily lose track of active cursors, always check CURSOR_STATUS before operations to avoid those 4AM "page-not-found" nightmares.
Optimize resources: Why deallocate an already closed cursor? Avoid this silly redundancy and save your database the effort.
Prevent error pile-ups: Avoid redundantly declaring the same cursor, cause that's like calling "shotgun!" when you’re the only one in the car.

Error handling isn't as scary as it sounds

Embarking on a journey with cursors? Here are some tips so you don't get lost:

Conditional operations: Use CURSOR_STATUS inside an IF statement. It's like the GPS for your journey so you know where to go (and where not to).
Deallocate intelligently: Ensure cursor openness before deallocation. Think of it as the Elvis check: "Has it left the building?"
Template checks: Include checks in your cursor templates - so you won't have to call Sherlock every time an issue pops up.

Practical applications of cursor status

Prevent accidental cursor reallocation

Not sure if a cursor was previously allocated? Running CURSOR_STATUS can stop you from unwittingly "double booking" the same cursor:

IF CURSOR_STATUS('global', 'MyCursor') <= 0
    BEGIN
        -- Safe to allocate MyCursor. It like reserving your seat at the movies.
    END

Nested procedure handling

Nested procedures can be like a game of pass-the-parcel with cursors. Before attempting any alterations, it's wise to confirm cursor status:

IF CURSOR_STATUS('local', 'MyNestedCursor') > 0
    BEGIN
        -- Safe to operate on MyNestedCursor. It's like asking permission before borrowing your friend's stuff.
    END

The Dynamic SQL combo

In dynamic SQL, you cannot directly call upon CURSOR_STATUS. Instead, transport the status into a variable and pass it to the dynamic SQL context:

DECLARE @cursorStatus INT = CURSOR_STATUS('global', 'DynamicSQLCursor');
EXEC sp_executesql N'SOME DYNAMIC SQL', N'@status INT', @cursorStatus;
-- Think of this as including driver's license with your rental car application.

Mass clean-up in testing environments

For testing cycles or situations with multiple cursors, use CURSOR_STATUS in a loop for a thorough house cleaning job:

WHILE EXISTS(SELECT 1 FROM sys.cursors WHERE CURSOR_STATUS('global', name) > 0)
    BEGIN
        -- Deallocate cursors. It's like your mom telling you to clean your room.
    END