How do you simulate a deadlock for testing purposes

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How do you simulate a deadlock for testing purposes..

Answer / jay

Below is a quick recipe for a dead lock. Two transactions,
one first updating table 1, then 2 and the other one doing
it in reverse order.

Both transactions wait in the middle for 20 seconds to give
you some time to execute them 'simulaneously'.

When you run the two in transactions in two windows 'at the
same time', you'll only have to wait ~20 seconds, and one of
the windows will experience a dead lock.

CREATE TABLE t1 (i int);
CREATE TABLE t2 (i int);

INSERT t1 SELECT 1;
INSERT t2 SELECT 9;

/* in one window enter: */
BEGIN TRAN
UPDATE t1 SET i = 11 WHERE i = 1
WAITFOR DELAY '00:00:20'
UPDATE t2 SET i = 99 WHERE i = 9
COMMIT

/* in a second window (another transaction) enter: */
BEGIN TRAN
UPDATE t2 SET i = 99 WHERE i = 9
WAITFOR DELAY '00:00:20'
UPDATE t1 SET i = 11 WHERE i = 1
COMMIT

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