Below is a SQL statement inside a stored procedure (truncated for brevity):

SELECT * 
FROM item a 
WHERE a.orderId NOT IN (SELECT orderId FROM table_excluded_item);

This statement takes 30 seconds or so! But if I remove the inner SELECT query, it drops to 1s. table_excluded_item is not huge, but I suspect the inner query is being executed more than it needs to be.

Is there a more efficient way of doing this?

mysql sql query-optimization
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