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CREATE TABLE t1 (f1 BLOB) ENGINE=InnoDB;
INSERT INTO t1 VALUES (NULL),('abc');
SELECT f1 FROM t1;
f1
NULL
abc
DELETE FROM t1 WHERE f1 IS NULL;
UPDATE t1 SET f1 = 'xyz' WHERE f1 = 'abc';
SELECT COUNT(*) = 1 FROM t1;
COUNT(*) = 1
1
SELECT f1 = 'abc' FROM t1;
f1 = 'abc'
0
CREATE TABLE t2 (f1 BLOB) ENGINE=InnoDB;
INSERT INTO t2 VALUES (NULL);
SET AUTOCOMMIT=OFF;
START TRANSACTION;
UPDATE t2 SET f1 = 'abc' WHERE f1 IS NULL;
SET AUTOCOMMIT=OFF;
START TRANSACTION;
UPDATE t2 SET f1 = 'xyz' WHERE f1 IS NULL;
COMMIT;
COMMIT;
ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
DROP TABLE t1;
DROP TABLE t2;
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