Why do I get "A cursor with the name already exists"?

Cursor Scope 101

Decoding Cursor Scope

Think of the scope as the cursor's playground. Lock the playground by using the LOCAL keyword and prevent global mishaps. It constricts the cursor’s visibility to the current environment (batch or stored procedure).

DECLARE my_cursor CURSOR LOCAL FOR ...
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Because no one likes a bully, right?

Stopping Scope Conflicts

Avoid confusions, make sure all cursors in the playground are discreet (meaning, no two cursors with the same name). As global cursors do not always restrict themselves to their batch, an identical name could cause conflicts. Stay alert!

-- Declare your cursors as LOCAL. Why? Because we respect boundaries:
BEGIN
    DECLARE my_cursor CURSOR LOCAL FOR ...
END
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Implementing Local Cursors

Save some time and headache by making it a habit to use the LOCAL keyword for cursors:

-- Procedure 1
CREATE PROCEDURE Procedure1 AS
BEGIN
    DECLARE my_cursor CURSOR LOCAL FOR ...
    -- [...] greet your cursor and move on
END
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Here's the fun part: you can use the same cursor name in a different procedure, and there will be zero conflicts. Life's good, no?

-- Procedure 2
CREATE PROCEDURE Procedure2 AS
BEGIN
    DECLARE my_cursor CURSOR LOCAL FOR ...
    -- [...] bid adieu to your cursor and move on
END
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In Procedure1 and Procedure2, my_cursor is playing peacefully without throwing any tantrums. Thanks to the LOCAL keyword.

Mastering Cursor Etiquette

Set-up and Clean-up

Your cursor life cycle should end as gracefully as it was initiated.

1. Finish up: Run CLOSE to end your interaction with the cursor.
2. Pack up: Run DEALLOCATE to release the cursor's resources.

Uniquely Yours

Avoid naming conflicts using these simple measures:

• Distinct naming: Keep your cursor names specific.
• Prefixing: Use procedure or module names in the cursor names.

Be a Sherlock

Keep track of those mischievous cursors using SQL Server Profiler or Extended Events, to make sure they don't mess up your database.

Error handling

Maintain sanity in your code by implementing TRY...CATCH blocks to tackle unexpected errors:

BEGIN TRY
    DECLARE my_cursor CURSOR LOCAL FOR ...
 	-- [...] yes, the same cursor again, no, we are not bored
END TRY
BEGIN CATCH
    -- Bazinga! An error just turned up (laughs in Sheldon)
END CATCH
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Error! Cursor Not Found

Dealing with Dynamic SQL

If you're using cursors within dynamic SQL and executing with sp_executesql or EXEC(), remember each execution is a new scope. Use LOCAL keyword to keep things under control.

Transactions and Cursor

Opening a cursor inside a transaction and closing it outside can lead to many a puzzling error. You need to be a step ahead, watching the transaction boundaries.

Nested Procedures

Every nested saved procedure is like a Pandora's Box. Inherited cursors, if not handled well with LOCAL, can lead to subtle redeclaration errors. Have fun, but don't forget your boundaries!