https://bugs.mysql.com/bug.php?id=77135

以下版本修复

Noted in 5.5.46, 5.6.27, 5.7.9, 5.8.0 changelogs.

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CREATE TABLE `test_bug` (
`a` varchar(50) DEFAULT NULL,
`b` text
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
insert into test_bug (a, b) values ('start trail', '');
update test_bug set b = a, a = 'inject'; -- 等价于 UPDATE test_bug SET b = CONCAT('inject', SUBSTRING(a,LENGTH('inject')+1)), a = 'inject';
select * from test_bug;

ITPub博客

Updating varchar and text fields incorrect results